Here's what we do as a 10 man.
Stack when MCs are being cast and have one tank announce who they are interrupting. Tanks can't be mind controlled initially.
Everybody else interrupts the other MC.
For what it's worth we just use a single AoE stun in P2 and cleave MCs down. When MC is empowered we use what I mentioned above, but swap to the targets because they have a lot more health.