I *always* consider Wasteland a spell when counting a deck's mana. (That's why I went to 18 swamps. The curve being so low is the only reason you can get away with so few lands, relatively.)
Funny that you're backing off of Wasteland when I'm warming to it. Kills
Maze of Ith, duals, Dark Depths, Mutas & Factories... those are either otherwise impossible to handle or pretty tough to handle with sorcery-speed removal. Since the deck slow-rolls with massive disruption at low cost, I think they fit.
Have you been perhaps playing a lot of basic-heavy decks lately?