I've checked around, couldn't really find anything on this, but here goes;
I've tried this and worked successfully on two bosses; Pathaleon the Calculator & Blackheart the Inciter so I'm guessing it goes for all NPC MC abilities.
When you get MC'd spam your SIT key, which will cause your char to spam sit down and not cast/melee on people. It can save you wipes, honestly.
This is for PVE purposes only.