If you have a Crowd Control (CC) ability, then make it known to the party when you first reach the dungeon. Sometimes a Tank will need somebody to SLEEP a bad guy to help with the mayhem. Let the Tank select which baddie needs to be temporarily disabled.

Since we can become all of the Classes in this game you can't assume that a Damage Dealer (aka DPS) character can't heal. Or that a Healer can't Crowd Control.

Therefore, it behooves you to learn a number of other Classes so that you can to take advantage of the cross-class slots that become available as you level-up. This is a really cool feature.