My guess is that a lot of people think a mob trapped in a whirlwind or whatever means 'time to hit this guy because he can't fight back!'
Rofl! This happened when i was on my sorc healer for Group finder Explosive conflict. an extra pack of mobs were aggroed by accident so i proceeded to cast whirlwind on one of those battlemaster guys. there were plenty of gold and weaker adds running around. the battlemaster was spinning around for a good 2 seconds and then the mercenary beside me started casting tracer missile. The projectile flew out and and i slooowly saw it flying to the direction of my cc'd battlemaster .
Not only that he continued to blast the said battlemaster all by himself... rockets versus bullets... through out the fight! He was so determined it actually made me lol in the end. The group was finished clearing up the gold mobs and he was still battling the battlemaster 1v1 by himself >_<. That PUG only lasted about 2 attempts into Story mode firebrand and stormcaller