It looks like Inferno is going to be pretty hard. (discussion about the inferno difficulty. It starts at 54:33 and lasts about 2 min)
My question is whether this difficulty is supposed to be feasible in solo, or will you absolutely need a group to solve it? If so, will it still be easier to do it as a group? I can imagine monsters with very strong resistances, so having a group can bring flexibility in your style of combat.