As of trying to duel a level 160 doc in arena, one thing strikes me. He can't be killed 1 on 1. I'm not usually the whining guy, and I don't cry because I lose a duel (actually, I haven't yet, so I wouldn't know), but it's totally impossible to kill him. No matter what nuke I use, I hit him for about 1100 damage. I assume that's fairly close to min damage, while it hits his 40% cap. As long as he can use Lifegiving elixir, he gets healed for 1000-1200 usually, and we're back to scratch. If I am lucky enough to get in two hits before he heals, he uses Complete Heal, and is back to 100% again. We would pretty much go on forever like this, since I root him out of his range, and he heals away my nukes.
I would assume this was a glitch when they introduced the new PvP caps. Could be it was intentional to make docs the most uber PvP class, but it doesn't seem logical to me.