There's two main reactions about this change.
1) It's absolutely horrible and takes away what differentiates "Brilliant" players from "Good" players. Through careful OGCD/GCD usage and some teamwork going on with a bit of common sense, you can swing a match in your favour. Now they're taking away so much, it'll be a miracle if things actually die before culling 5 (purely dependent on the healer PvP actions) and if the fights are even half as entertaining/engaging (spoiler: they wont be). Spamming 1111/222 until you get to press an extra button every 15 seconds isn't engaging at all. It feels like it's catered to the "casual" players that are stuck in Bronze/Silver and can't perform a full rotation correctly.
This sentiment is shared with the actual core PvP playerbase in this game who have played their fair share of matches and have a good understanding of how to win.
2) It's great because now I can finally be great at PvP and everything will finally work out for me! It's this whole games' combat system in PvP that was holding me back the entire time, it wasn't my fault at all! Now that they're got rid of the secret sauce only the few hundred core PvP players were using, we'll all be able do the same thing and I'll get my deserved spot in the rankings! Amazing!
This sentiment is mostly shared with the players who aren't actually at a "True Diamond" skill level. 90% of these players are probably stuck somewhere between Bronze - Gold.
The reason I say "True Diamond" is because anybody can just easily get Diamond now. The highest rank in the game isn't an achievement anymore if someone with a 40% win rate can get it.
Final Note
This all being said, reducing bloat is a good thing but not at the expense of pruning your game mode until it's as brainless as spamming a handful of buttons. I would say at least add a few extra PvP abilities in.
Looking at the DRG example they used in the live letter, I can tell you 100% it's impossible for it to even come close to solo-ing a half decent healer now. Removing such damage potential from a Job makes it stale and boring. For those that doubt me, I know you'll agree the day you're playing and your co-dps is spamming 1 combo all game on the wrong targets. You won't be able to kill a single thing.
If anything, they need to be more transparent with this and show us all the abilities/actions for each job in PvP, especially healer actions. We'll be able to know seeing the potencies/actions what changes need to be made.