It's also not hard to simulate a 2 player game by playing 2 divisions.
I plan to play primarily solo, and my first games were solo with two divisions. I plan to try three at some point, but that might be a bit much.
Knowing when to help other lanes via troop/division abilities and instants is a big part of the game, IMHO. The nice thing is that the game lends itself to near total customization in terms of difficulty. It's not like the game is going to break if we swap a few cards in or out while tweaking things. Cool design.