You will need a lot of buttons to do all that.

I'd just go with /assist and fire 3 hex's at the mob you want to cc, then get back to whatever mob you want to dps, and use an aoe to keep the other 2 on the tank (as you are not dpsing them tank should keep agro I assume if its like EQ). Or you could

/targetenemy
/cast hex

and hope to hex a bunch of mobs and with luck the one you actually want to cc, heh. One shaman could have /targetenemy 1 so he is sure to get a different target then the other.

Thats not to say you could not set it up as you want but seems just to complex to get 2 extra seconds of dps from two of your dpsers. It wont take long to cast 3 hex on the mob you want to hex and then get back to dpsing.