I've only played about 50 games or so, but I've had major success with:
Lich - reach level 6, ult, automatically get double kill; Earthshaker - OP AoE stuns; Enchantress - Insane heal with incredible AI and her ult is hella strong. Nature's Prophet - Global presence with a non-ult ability, and ridiculous global nuke with over 9,000 bounces.
Sadly as much as I like Lich I think I need to drop him since he's really been tanking my W/L ratio. It's not really that I'm doing badly with him myself, in fact I think a support role like his fits my preferred play style the most. The problem is he really doesn't seem to have the ability to just dominate a fight and make up for my team mates' faults like the other two. Seriously, when I'm playing Axe and Sven I'm generally unconcerned if I look at the scoreboard and find out someone's feeding or has D/Ced, because I know that so long as I'm careful and don't get ganked I can potentially catch up. With Lich? Unless the guys I'm fighting are really bad I'm not going to be able to make a big enough difference.