I find though I still tend to get trapped a little in defensive mode on the back bar (especially when trying to hold a flag) and I'm regularly getting stun locked and bursted to death. I'm learning to be better, but it's hard to do at times and my reaction time still isn't up there.
I still run a fair amount of Heavy with Inpen though, so my Stamina is average but it doesn't feel like my sustain is too badly impacted.
But I will say this much, for the first time in a long while I'm actually enjoying doing PvP.
Whilst I'll get 0, 1 or if I'm feeling REAL nasty... 2 kills per game (usually defending a flag 1v1 or throwing a few jabs in a general melee situation), I get a larger number of of those awards for healing / defending that make it all worth while and often (on anything except Deathmatch) I'll usually place 1 or 2 on my team at the end of match screen which is very satisfying.
Now that I'm fairly comfortable with my gear load out, I'm moving more towards how to better use my environment (takes me back to my WoW Arena days as a healer) and whilst I'll still get caught out and stun locked / smeared, it's happening less now and I'm having a lot more fun with it.
Healing PvP in ESO is straight up harder than PvE. Humans will always be far more dangerous than AI PvE enemies and you have to think about more than just positioning and rotations to do well.
You have the tools, gear and skills to work with - but you're playing the situation and players more and overcoming that is a lot of fun and very rewarding.
Up until a few weeks ago I would struggle to get my daily BG out of the way for completion sake a couple times a week.
Now I'm finding I'll do it daily and a few more BGs besides.