Hey there,
I wanted to gather all the current bugs and problems that are bugging Sorcerer pets. Some rather known, some rather unknown.
I'm playing with pets since almost 2 years now and I believe or hope, that I can give you justified insight
Overall Problems:
Pets health is plagued by several bugs at the moment. Pets were supposed to gain 5000 health in Cyrodiil and they do

But the problem is, that pet health was reduced at the same time. Since this was not mentioned in the patchnotes, this must be a bug. See Pics below:

The Twilight used to have over 10k health in pve, now only 7k. Every scrub will agree, that something with 7k health is not able to survive anything in pve


In PvP it has 11k, so the intended 5000 only result in roughly 1000 more health than it used to be prior to this update.

The familiar was hit even harder. He used to have 21k health in pve, now only 16k. Since the decrease in health is different on all pets, I believe this is an unintended bug and not a structured change. These values are just weird


In pvp, it now has slightly less health than it used to have prior to this update.
In addition to that, pets (once they've been in combat) no longer seem to be able to heal themselves over 77% of their health with their HoT.
And now probably the biggest problem: Pets are still the only abilities in the game that are not affected by Champion points. This was acknowledged by Ericus Wrobel in an Eso live show

this should have been changed with DB in my opinion. Pets must be affected by elemental expert, elfborn and spell erosion.
Individual ProblemsThe Storm Atronach
My biggest child and the one what worries me the most

Atronach spends 8 seconds of his 28 seconds duration doing nothing(provided you take the greater storm atronach)
When you summon it, it has to create itself first and this takes almost 4 seconds. These 4 seconds already count towards its duration.
Addionally, the Atronach makes 4 small breaks during his duration, each being roughly 1 second. So he spends 30% of his duration doing nothing, think about that

Every good DD can tell you, that 8 seconds of no incoming DPS is poison for your dps, turning this Ultimate into an invalid DPS option.
The Atronach either needs to get his cost reduced, his behavior changed to attack instantly and take no breaks, or have his duration increased.
The Atronach can't move and is CCable. Its ability to break CCs after 5 seconds is still not a good solution, an Ultimate shouldn't be THAT easy to counter
Look at Molag Kena's Atronachs.... They slowly move and are not CCable. Why don't you give Sorcerer the exact same copy of these things ? (without the explosion of course ahahahaha

)
Daedric Prey
Simple thing. If you combine velocious curse+pets, the damage you cause will be significantly higher than the damage you cause with Daedric Prey+Pets.
As Pets currently lag any serious damage, increasing daedric prey's buff from 55% to 80% seems to be a reasonable solution.
Conjured Ward
Since this ablitiy was nerfed, this ability has taken a hard hit in terms of use for pets and it has become significantly harder to keep your pets alive.
It offers no support for your pets besides some protection. Conjured ward and its morphs should regain the 25% pet damage buff they used to provide and maybe grant pets a minor protection buff.
The concept of the summoner is great, you use a shield to support your pets. Please encourage this.
Twilight and Familiar
My Babies at least, they are cute, aren't they

? Well, I fear being cute is their main strenght
The Twilight Tormentor is what worries me the most. 50% more dmg vs targets above 50% health is not only a weird concept, but also a rather bad one

Making its ability useless for 50% of the fight.
A more usefull and reliable solution would be, to increase its damage based on the health percentage of the target.
Starting at 100% more damage vs targets with 100% health. 80% more damage vs targets with 80% health, 20% vs 20% etc etc

So the overall damage increase of the twilight will be 50% and it remains usefull the entire fight. Right now, the Twilight Matriarch is the only viable morph option for this.
The Volatile Familiar
This ability should become an easier option for DPS. You have to reapply its effect every 4 seconds. This is very bad and a disadvantage for DPS.
It should pulse over 8 seconds and each 3rd pulse should be able to stun (as it is right now basically)
The Daedroth (Maw of the Infernal)
(not my picture)
ZoS was trying to make this set viable since quite some time, yet it doesn't seem to work. This set is one of these sets, that you just can't overbuff as it is right now. You don't need to be so carefull here

This set is just super bad.
Its proc chance must be signficiantly increased. Even spamming lightning staff heavy channels don't seem to proc it frequently.
Its duration must be increased to at least 25 seconds.
Health on the first piece is not usefull, we already have other monster sets granting this bonus.
Right now, I loose lots of Magicka and spell damage if I want to run this set. Its first piece MUST grant Magicka.
And lastly, it needs another speed or range buff. Its fire breath doesn't even seem to be able to hit slowly moving targets in pvp and pve
Passives
Rebate: Most useless passive in the game. We have hard times keeping our pets alive and the reward for seeing them die is fairly small.
Rather than restoring magicka when a pet dies, it should restore 0,5/1 percent of your magicka, when your pets deal damage to a target and this has a cooldown of 1 second.
Maybe even 0,5/1% stamina to make this interesting for stambuilds and tanks.
Summoner Expert: The health bonus from this passive is not usefull at all for summoners. Nightblades get 8% Magicka for free basically, Sorcerer needs to sacrifise 2-3 slots in order to gain that. Giving max magicka to this passive is not only fair, but actually usefull and that's how it should have been in the first place

So and that's it for now

I have not brought up all my suggestions, as I wanted to keep this thread focused on Pet problems and bugs.
I hope this text wall didn't give you cancer. Auri-El bless you all (except when you are DC or EP of course, Lorkhan get you)