I think that ESO has become the premier example of development and technical debt running amok. Over time, they coded themselves into a corner, and now don't know what to do to get themselves out of it. In my opinion, the problem isn't the "end game" players who have become experts at the rotations, combinations, and the proper use of skills. That's the nature of any game. Where ESO went wrong, and I would urge the developers and product owners to take a close look at this post, is the approach they are attempting to rectify the problem. The answer isn't to "NERF" the world. That only will make the 95% players even more frustrated as they spend gold, crown store coins, and grind away to become better and then get it all yanked away.
The issue, surrounds the levels of the end game players and how they have approached the game. There was never any intent for someone to walk into VFL or VSCP with 4 DPS and simply burn the bosses faster then their respective mechanics could work. Oh, just send in 4 players each pulling 75K+ DPS and give them a shield -- Don't worry, the boss will be down in 20 seconds anyway...
Go back to the drawing board on your nerfs, gear changes, weapon changes, skill changes, etc. Think about how you actually wanted to evolve the game. Make the DPS buffs trigger off of actual tank actions -- Make the healing / buffs /etc. trigger off of healer actions. Make the game go back to where it's not just where you can deal the damage, but also work with coordination with your team to support and mitigate damage, sustain, and win.
I came back to this game and have been playing it for quite a while. It has evolved. But no where in what I see ESO doing have I seen their taking any responsibility for any of it. They are the ones who created the DLC trial and dungeon content, the hard modes, and then created the awards and achievements to drive players to find every single way to get around them. So, you created the monster, and then you come around and are going to make it where you will have to add a CP300 cap for Vet Fungal Grotto?
Make your changes to force the coordinated mechanics. Make your changes to require the team aspect in the dungeons and trials. Think about your technical debt and fix it. It may take a bit longer then you want to, but in the end your going to have a more viable product long term. Do a better job on quality control. On the trials, I've seen more bugs, crazy actions that make no sense by bosses and critical characters (fighting through walls), etc. You can't tell me you didn't see some of this stuff.
Stop taking the easy route of invalidating entire tree's in the CP chain. Let them do what they were intended. Fix your real issues which is the allowance of a game ran only on how you can rack, stack, and pack your cancels on top of who is running what sets on top of what sets and how fast a select few can animation cancel. This game was never supposed to be solo played.