Primal Carnage is now £1.39 on Steam. Thanks macleanie!
Evolve isn't the only asymmetrical multiplatyer game on the market, and in fact it's pretty late to the party. Plenty of games already offer exciting gameplay between carefully imbalanced teams, and Primal Carnage delivers some seriously enjoyable dinosaurs vs human showdowns. The sequel is out later this year, but you can currently get the original for just £1.39 (a massive saving!) and I believe that you'll also get a 50% off voucher for Primal Carnage 2 into the bargain.
Note that Primal Carnage was recently in the Blades Of Janus bundle though, so check your backlog!