Even if they have life steal, most carries can't deal with 80%-100% thorns, so they may not attack you, but when they are stunned and forced into a cage with just you, what else are they going to do? Be cc'd (essentially) for 5 seconds? Also, its not hard for most Str heroes to be much tankier than carries, especially in pub games. Not saying Clockwerk fits well into the current pro meta, and I did not watch the game, but he's a fantastic ganker and initiator.
Edit: Damn, I really can't wait for the International to happen so they can release some of the newer heroes I haven't experienced because I stopped playing DotA1 years back. So many of them sound unique and interesting, and still missing heroes like TC, Centaur, Soulkeeper, Magnus, Troll, etc. Bah.