They already have a top Protoss on their team. Though MC would've made a great PvP partner for HuK. I feel like they need better Terran and Zerg players to round out their roster.
(I feel as though Machine, Axslav, InControl, are strictly b-teamers)
They have Puma and DeMuslim for terran, which is solid. I guess another terran would be nice, but imo another zerg would fit better. Machine hasn't been able to demonstrate he can perform against top players (US, Euro, or Korean) and StrifeCro's success is solely focused in 2v2 matches.
I wonder why most of the top US BW players haven't translated well to SC2. Perhaps it's due to the explosion of the game: whereas in BW they were mainly dominating their local scenes as well as US WCG, now there are far more players from around the country, many on teams with Europeans or other foreigners. In short now that the talent pool is bigger they no longer stand out
Interestingly they're still dominating small, local lans as they did in BW; Machine and InControl regularly win small events in Arizona for instance.