When to face Diablo?

[gimlisam]

Actually, I've been wondering the sme thing with my Dentist. He is level 27 right now, and has yet to do the Hellforge quest. Should I get some levels? He does 40-53 damage, iirc, with teeth, and is trying to boost his Bone Prison right now (level 2 with ~8 in synergies (mostly wall for added teeth damage.)) He has good, nay, great resists (for me), with the lowest (fire) at about 48%. Duriel was very hard for him, but meph seemed much easier, even though it took about the same amount of time, I would say. That said, is taking on Diablo soon a good idea, or should I try to gain some levels?

GimliSam