The key thing in a lot of the changes we are making is diversity, so that players have a lot of different options and a lot of different cool builds that they can make, and that all of those are useful and effective in terms of "I can get good healing I put for this" or "I am doing a lot of damage when I'm doing this type of build".
- Eric Wrobel

We want you to manage resources, and have that be a choice. Right now, on live, that isn't a choice, and so you can go full out damage, full out burst, and you don't really have to trade anything for that.
- Rich Lambert

First of all, I agree with these goals 100%. And I also firmly believe that feedback needs to take the stated intended goals of the development team into account, to assess how well these goals are met. As such, I'd like to reflect a bit on diversity and choice in ESO's character system.

Diversity

Something Rich touched on during the same ESO live stream is that currently, the way to deal damage is light attack weaving with a spamable skill, in combination with a rotation of DoTs. While these are not functionally very diverse, at least the different classes each bring something unique to the table. Heavy attack builds have always been kind of niche, but will rise in popularity with the upcoming changes to sustain. And that's a good thing for diversity.

But the issue is: Heavy Attack build means Lightning Staff build. While I have seen promising parses for stamina HA builds, the range, cleave damage and AoE damage boost of lightning staffs is unsurpassed. Certainly in terms of fun: Discharging your lightning staff into a crowd is much more satisfying than all the other heavy attack types, which feel very bland, and I'm already one of those weird guys who like heavy attack builds. It should really be noteworthy that lightning staffs are the most unique of all weapons in this regard, and I'd like to suggest reviewing other weapons' heavy attacks to promote the goal of diversity. To give you an idea what I'm talking about, here are some suggestions. Note that these are not primarily designed with balance in mind.

• Lightning Staff: Keep as is.
• Inferno Staff: If your heavy attack is the killing blow, the target explodes and deals the heavy attack damage in a small AoE around it (3-5m).
• Frost Staff: PBAoE channel. Plant your staff into the ground and summon a small blizzard around you. The current taunt mechanic is clunky for tanks and detrimental for DDs, and a PBAoE attack would keep the spirit of a more defensive element as you'd have to stand in the middle of a crowd for the most effect, as opposed to the ranged staffs.
• Restoration Staff: I'd consider keeping this one as is. It already has major mending, which complements healing builds well.
• Two-Handed: The Forceful passive now deals 50/100% damage to 2 nearby targets. Compared to lightning staff, which also has the range advantage, this seems like a modest buff, and keeps the vision of this weapon by improving an existing passive.
• Dual Wield: Another 40% damage against low health targets.
• One-Handed and Shield:. Evades the next attack while charging. Like a parry, and helps tanks sustain with heavy attacks without getting interrupted.
• Bow: Deals damage to all enemies in a 2xMax_Range meter area in front of you. Bow heavy attacks are already unique in that you can hold them, but now you can hit multiple targets if you position correctly.

Now, while improving the viability of heavy attack builds is surely a good thing for diversity (that is, as long as they don't outshine weaving light attack builds - be careful here, ZOS! You already suggested adjusting the ratios for light and heavy attacks, and I think it would be prudent to increase LA damage and decrease HA damage by a bit), we still have effectively only these two playstyles.
Therefore, I would also like to suggest to bring a third option up to par that I feel has been underdeveloped so far, and that are builds that focus on enchantments. Enchantments are kind of the anithesis to the sustain-focused gameplay, as they don't come at any cost (but also don't replenish a resource like heavy attacks), as well as the damage-focused gameplay, as their damage can only be increased through champion passives.
I think enchantment builds could be made worthwhile by improving on any one of these points:

• Improve damage of enchantments: This would best be done by improving the Infused trait. Other damage-focused builds currently use Sharpened, and being forced to forego that trait in favor of Infused would best serve to balance enchantment builds against other damage builds.
• Decrease cooldown of enchantments: To the point where every attack would yield a guaranteed enchantment proc, i.e. 0.9 seconds IIRC. This too should probably achieved by improving Infused and/or the Torug's Pact set.
• Add AoE capability: Either by adding a new item set that would proc enchantments in an AoE around the target hit, or all new enchantments so you'd have to chose between single target and AoE enchantments.

The goal would be a rotation somewhere between light attack and heavy attack builds, were you apply DoTs and then either just spam your light attack to proc your enchantment, or weave light attacks with other skills if you have enough resources. In effect, it's a light attack buid that shifts damage from skills onto light attacks, thus requiring a bit less sustain and a less demanding rotation. The downsides are no resource recovery from heavy attacks, no access to poisons, and lower overall damage from other sources (as well as possibly no AoE capability). This would broaden the diversity of possible builds, as well as give players who don't like heavy attacks another sustain-friendly option.


Choice

Meaningful choices are probably one of the most important staple of RPGs. You can't play a role if you aren't better at something than other roles, which also means you are worse at others. You have to chose.
There are lots of things you might have to chose between. Sustain, damage, healing, defense, mobility, utility - all of these and more should have drawbacks (I wrote a more detailed post about how adding more attributes would help differentiate between these roles about a year ago).
For now, it seems ZOS wants to focus on the choice between damage and sustain. So, let's look where in the game we actually have to make a choice between them.

Skills
Skills compete with each other on two fronts: Morphs, and a place on your skill bar. The former is only the case in a few instances - e.g. Whirling Blades vs Steel Tornado. The latter is almost never the case, as there is a limited amount of damage abilities you can make use of. At a certain point, there's just not enough time in your rotation to use more abilities. So you are almost always free to slot both damage and sustain abilities without any issues.

Armor Type
The armor types have always struck me as a bit odd. Light armor is good for magicka damage and sustain, medium armor is good for stamina damage and sustain, and heavy armor had a wild ride from anything inbetween. Initially it was probably designed to be a choice between damage (light or medium) and defense (heavy). However, as shields are an excellent means of defense and resistances are easy to cap, sustain became more important. Therefore, there's not a lot of choice involved here, except in instances where heavy armor provides superior sustain to light and medium armor.
I don't have a good solution for this one, sadly. Personally, I think damage should not be a factor in armor passives at all. For one, it doesn't make a lot of sense, and it doesn't enforce a choice between damage and sustain. Instead, I think it would be prudent to balance the different armor types around other factors, namely sustain, defense and mobility. This would further open up diversity by allowing magicka builds wearing medium armor for mobility, or stamina builds wearing light for sustain. The problem is that weaknesses like bad defense or lackluster mobility can be overcome with skills, such as shields and Streak or Major Expedition buffs. So this area is a bit harder to restructure to enforce choices, and should probably wait until other changes have been made.

Champion Points
The nature of the champion system makes it impossible to chose between sustain and damage. By its very design, i.e. split point pools for Thief/Warrior/Mage passives, you can have it all. Currently, when I want to spend a champion point, I chose between magicka and stamina builds, not damage and sustain or defense. If you truly want to enforce choice, the champion system has to be restructed, so you don't have to chose between magicka and stamina, but between sustain, damage or defense within a given constellation. For example, Mooncalf and Mighty would have to be in the same guardian constellation (Thief, Warrior or Mage).

Gear
This is the only area where you are actually limited by the number of your gear and enchantment slots, so players should theoretically be forced to chose between damage and sustain. And you correctly identified that people did not need to do that, because there were enough sources for sustain outside of gear (certain skills and champion passives), so they could focus their gear entirely on damage. While I think the adjustments you made have gone a bit overboard especially for group buffs and synergies that served to improve resource sustain, the approach is sound: You remove bonuses from areas where players don't have to chose, and load them onto areas where they have to chose. This way, the lost bonuses can be regained, but only by chosing the right gear at the expense of other gear.
Consequently, I would have expected a reduction in base recovery rates, and an increase in the recovery bonuses from item sets and enchantments. Should overall sustain prove to be too low after all, I think increasing these bonuses on gear would be the best mitigating approach that enforces choice.
Also, again, I feel enchantments have been overlooked, namely the Drain Attribute enchantments. Currently, they deal damage and recover a small amount of resources. In this new meta, I would suggest to remove the damage component, and substantially increase the attribute recovery component, so the choice between damage and sustain is enforced in this area as well.

In summary, currently, there is not a tremendous amount of diversity or choice. Lightning staffs dominate heavy attack builds, and choice between damage and sustain is mainly confined to gear sets.
To promote the intended goals of diversity and choice, I'd suggest to

• Restructure the champion system to actually enforce choice between damage and sustain
• Improve heavy attack builds by differentiating weapons' heavy attacks, making these builds more fun and diverse
• Lift enchantments from a niche build to another option alongside light and heavy attack builds
• Keep these three playstyles - light attack weaving, heavy attacking and enchantments - on par, e.g. by increasing LA damage and decreasing HA damage
• Focus on the area of most choice, gear, by increasing bonuses on items when you reduce them elsewhere

While making enchantment builds viable is a bit of a personal wish of mine, I see restructuring the champion system to enforce more choices as the most important point, followed by improving the diversity and fun of the now made viable heavy attack builds.