I have no experience with any class over 20(aside a 22PLD) besides my Priest, but it's durability is quite astounding.
While my point build is likely heavily retarded(Disc/Holy/Shadow! lol) it seems to do very well for me right now.
With the +Inner Fire defense and +Holy damage, I've been able to take on a lot of crazy stuff.
Most recent, and proud accomplishment, was I just solo'd the Summoning the Princess(Group) quest at level 46. The recommended level is 50 with two people, but I didn't feel like shouting in UC forever hoping to get someone so I tried it alone.
It was intense. I pre-buffed PW:Shield, Inner Fire, and PW:Stamina. Got full MP/HP and summoned. Tossed on PW:P, Plague, and Holy Fire/Mind Blast/Smite. If you've done this, you know she spawns a TON! of elementals, all about 45+. Tossed out a total of two Fears and used both Renew(full points), Lifeblood(rank4) Desperate Prayer and a single Greater Healing Potion and my sliver of HP let me fire the kill-shot of a Holy Fire.(I died right after. Damn elementals!)
But all in all, it was FUN! I can't wait to try more group things solo :)
Please, post any solo Priesting you've done that made you go "Woah. FUN!"