Very easy to solo as a sentinel, just use doc. and rotate between using interrupts (force leap if specced for it in watchmen), and defensive cooldowns when you don't have anything to interrupt it with. stim up, and use your 20 minute cd if you have to. Took maybe 4 minutes as a level 38 sentinel. Honestly, i found actually getting to the area through all the elites/champ mobs harder than the fight to him.