Just as long as any other class. The issue here is that the ranged classes can play smarter (e.g., kite better) or just suicide run. They can get by with non-optimal gear.
My Wizard has ~60k HP, ~5500 buffed Armor, ~700 buffed resists. It's not like that gear rained from the heavens. Gearing appropriately for any class takes a lot of time (or luck or gold). This is part of the whole rationale behind the repair bill increase; to stop trying to revive zerg down content (or skipping things) and just farming where you're comfortable clearing.
Inferno progression is meant to be slow. The "I've been farming for a week and barely made progress" is the expected norm, not the "it's been three days, I'm on Act 4" that some people were able to do.
Basically, take a look at the progression that the Hardcore players are doing. That's the intent, though a little extra farming so they don't get killed at all. And even they are going faster than Blizzard envisioned (granted, goblin farming).