When to face Diablo?

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I have a SP 1.10 MA/Shadow Disciplines assy, who is currently lvl 26, and just about to start act IV normal. The goal right now is to get at least to lvl 30 before facing Diablo. My stats are :

(with items ) :

59 str
54 dex
38 vit
base energy

39 saved

13 CM
1 BoS, shadow warrior, mind blast
1 in each prerequisite
2 FoF (eventual synergy for PS)
3 CoT (eventual synergy for PS)
1 BoI (wont put any more here, will just synergize the other 2)
1 TS
1 CS
182 life
78 mana
321 stamina

Resists :

Unsure. Fire is 50-something, lightning is REAL low, gotta get it up. Others are kinda low, except cold.

Equipment :

Nothing special. No uniques, and only set item I'm wearing is vidala's fetlock. Also have death's guard sash in stash for cannot be frozen.
How high clvl do you think I need to face Diablo? I have had a LOT of problems with andy, duriel, and meph so far.

Thanks all.