If your goal is to win first and foremost, why wouldn't you use the best heroes in the game? DotA will never be perfectly balanced, no game will, and the pros are going to be the best source of information more often than not. I don't really blame them, they're just trying to play their best, even if it makes the game boring for everybody. I blame Valve for not releasing balance patches often enough. They should be nerfing push strats already before they ruin the Shanghai major, and more consistent balance patches would throw public players out of the loop often enough - by the time they had a chance to copy the strategies the pros were using they'd be nerfed.