I did some DotA2 streams too, using a E8500 @3.8GHz (i think its quite similar to your processor)
I have to say, that the stream runs better (more FPS in game) if you decrease the shadow quality (low), turn off AO, turn off fog and water quality. Also I turned off the portrait animation and ambient creatures.
Settings I would let running: Specular, specular bloom, additive light pass, world lightning -> because I experienced that the difference between your vision and fog would be less (low contrast imo, that kinda bothers me while playing).
Well I don't know which settings you actually use, but I just wanted to tell ya. You may even use more low settings.
But srsly. Just try it. Bad luck if it doesn't work, right? ;)