So in preparation for guest casting this coming Sunday Night Fight match between Symbiosis and aljaz, I spent a great deal of time watching replays and learning their playstyles. I decided I might as well put this information to use, and recorded a pair of videos highlighting their unique styles. Check them out and get up to speed before the games tomorrow!!
An i7 is overkill for streaming, an i5 3570k overclocked to around 4.5GHz is more than enough for 720p and can handle 1080p if you set things up right. You don't really have the bandwidth to stream 720p right now though.
You might be able to stream 480p at 15FPS. Try that with a bitrate of 500kbps and the preset set to XSplit Default. If that still kills your performance too much, you'll need to get a better CPU. Your upload is a bottleneck as well, but you definitely don't have the CPU power to stream 720p+ anyways.
Whatever you do, be consistent with it. I personally use 1 for vehicles, 2 for AT guns, 3 for sniper, and 4 for artillery, with slight modifications based on the game.
The strongest tool for multitasking, though, is the minimap. You should be looking at the minimap more than you look at the main game screen. CoH is a low unit count game, and those units are almost always spread out unpredictably. Focusing on the minimap allows you to instantly identify threats and quickly move to control your units in those situations.
Most players develop tunnel vision during engagements, and have a difficult time doing other things while units are fighting. You have to do other things while units are fighting. This notion is much more important than using control groups effectively when it comes to improving your multitasking.
I'd honestly be surprised if they didn't open up the beta to streaming and videos eventually, even if they never truly "open" it in that they let anyone participate. A beta that you can get in by preordering is essentially open, after all, and it gives them so much free publicity. It would be silly not to.