What are the goals of balancing the combat system in ESO? Following the process and patch notes over the past five years, it appears that a main concern is to rein in what can be done by the best players and groups ("more power than we are happy with", "how high it can get", etc.). However, I think such a focus would be a mistake. Rather, I'd like the focus to be on what can be done by a typical, average player and group. Actually, rather than a focus on "reining in" to begin with, I think a focus on "offering choice" would be more suitable and beneficial for the game and its players.
Combat balance is relevant only to those that are interested and regularly engage with vet and hardmode content. Even within this group (possibly a small fraction of the general ESO population, but idk the numbers) there is a huge spread in terms of knowledge and ability. These somewhat correlate with playing time, which for a more casual player is probably about the same number of hours per week that a more sweaty player plays every day. Many of the more casual players and groups do not get to the same level of "high power", not even close to it. Nevertheless, seeing what can be done with enough skill, time, and dedication gives them something to strive for, an incentive to get better at the game in various respects. Practicing, both individually and as a group, is slowly rewarded with better results, uptimes, damage, fewer rezzes, etc. This type of progression is very important in order to keep a mid and long-term motivation to come back to the game and replay the (same) contents, beyond just clearing them for one time and be done with it. For many casual players, it takes muuuuch longer to go through this progression than for the top players. But they will keep going, as long as they have fun, a large part of which is to feel a measurable sense of progress along the way. Thus, "reining in" affects not only the top players, but all players, by shortening the path along which they can enjoy progress and keep playing the game. Of course, if reaching the ceiling was completely trivial, this would be a problem as well. But triviality should be measured with a (maybe even slightly below) average level player in mind.
What makes a game fun? A key aspect imo is choice: The players should have a large of meaningful choices to make. For a round-based game it is important to not have too many choices each turn, or the players are overwhelmed and take forever to make their move. But for a real-time game this is not an issue. Combat in ESO has at least two independent parts: build (character, skills, gear, potions, etc.) and the real-time fight. Ideally, players have many meaningful choices to make in both parts. Fundamentally, this is the case in ESO. But every change in the combat system has the potential to destroy the balance between choices. So I think it should be a (if not the) main focus of combat balancing to maintain and increase the amount of meaningful choice. In order to be a meaningful choice, there are two aspects: (1) The outcome must have consequences. If I can't feel the difference, what does it matter? (2) All options must have their merit. If one is always better than the other, it is not really a choice. It is perfectly fine if one option is generally better, as long as all options have at least a niche, for a particular role or fight. Admittedly, such a balance is difficult to achieve and maintain. But I think it is much more important to make the game fun and engaging to play in the mid and long-term than balancing any collection of damage and buff numbers on a spreadsheet. (And this is not to say that these numbers are irrelevant.)
Unfortunately, some of the proposed changes in the latest patchnotes effectively destroy meaningful choices. That would really be a pity. Hopefully you can give these another look and come up with other solutions.
* The Arcanist class mastery script would become completely redundant due to Tome-Bearer's Inspiration. Some players in our guilds started building an arcanist char specifically to be able to play this signature script. Before they are even finished setting it up, we would have to tell them: Sorry, that probably was not worth your efforts.
* Many of the strong and unique class passives would become bland and redundant, by converting them to the same minor buff that can and often is easily obtained from other sources. The passives of the skill lines are very important to the function and feel of the character (cf. class identity) because in contrast to the skills, the passives are always active. So they are a deciding factor in the choice of skill lines to use. In the past each class had its own unique buff that could not be obtained from any other source. This was a very good way to make each class feel unique and meaningful. This uniqueness was already partially destroyed as a collateral damage to hybridization. It would be nice to address this issue and give the classes and skill lines some unique aspects, rather than a common minor buff, with a cooldown as a cherry on the top.
* The nerfs to Relequen and Coral Riptide seem unwarranted, given that these sets are hardly used in U46 anymore. I think it would make more sense to give them the same treatment as the other sets, say, Siroria, and slightly buff or at least keep the same the effects at maximum #stacks.
Finally, some of the skill lines are not a viable choice right now, for any role. So it would be very good to find ways to make them more attractive if only by buffing some numbers as a start, and in more interesting ways as a long-term goal.