I only can afford two acccounts also, but you don't want to do two shamans, you want to maximize CC, so with only two accounts I would go with this:

2x hunters, set your pets to one target and kill the other, this would be quite fast.

2x mages, set frost nova as round robbin to use it at different times, same with sheep. You might want to go fire while levels to 60 then respec to your desire.

2x warlocks, use the tagndrag method and take down 4-6 enemies at ounce easy. Set your pet attack at round robbin so your pet can tank 2 mobs, also set fear as round robbin.

2x druids, go balance, set entangle roots as round robbin to maximize CC, also I find if you set your first one as healing touch and the second on just hots (rejuve, lifebloom, maybe rejuve) for good heals, and after the second one casts it hots have it use starfire or wrath at your target, works great (so I hear, saw my friend do it).

I'm just giving my opinion, I've tried doing multiple classes and screwed up. maybe I just suck at it. But 2x shamans might not be the best choice :0