I've seen a jungling Windrunner in the competition to get into the 2012 International, she was set to go up against an impossible trilane, she saw her opponents then abandoned the lane and went to the jungle and managed to clear 1 creep camp for 1 level then had to go heal =p
Not the first time I've seen a 4-1-0 lane set up, but probably the first time it worked out well, all depends on how quick each team adapts to it.
I don't think there are any particularly imbalanced duos.
Besides Dark Seer, the Invoker is another one of those heroes that has synergy with nearly any other hero in the game. Come to think of it, Invoker and Dark Seer on the same team would be pretty funny... Vac + Tornado + Meteor + Deafening Blast....