Ok, so... I'm a veteran priest player. Hell, I would go so far as to say I'm the best battle priest on this server.
Here's my take on the issue:
You can't buff holy light damage anymore. With full gear and link my priest is popping off 300k+ holy lights. With this build I have approximately 220k hp... this means 1 maya reflect and I'm dead. Holy light build doesn't work well on this server other than warping into a pvp zone and randoming people then running away. In any legit battle/duel the enemy will just gtb/angeling/or even worse maya you and you'll reflect kill yourself in 1-2 holy lights.
Now, if you really want priests in pvp I say give them like a 2% chance at casting lvl 3 asura from strike eagle. Remove the 10% holy light damage from strike eagle because the priest book is for HL build, not the scythe. People seem to be reluctant of this because "well what if you auto attack someone with reflect?" It's called double FBH's. With two fbh you have so little mana that asura will do shit damage and you'll take very little reflect dmg.
Another thing that could be done is giving them improve weight limit like all the mages and even stalkers have. They don't need more hp but holding more seeds would be very beneficial.
TL;DR: Priests don't need more hp. I have almost 400k hp on my tank priest... I tank full asura with gtb/skolls. There are other ways to buff the class.