Slime Whip

Whips are summoner tools first. The reason to swing one is the tag it leaves behind, which drags your minions onto whatever you just struck, so you are aiming at the target you want dead rather than trying to carry the damage yourself.

This one layers debuffs on top of that tag, and the very end of the arc adds a burn that the rest of the swing does not. Getting the far tip onto an enemy is worth more than simply connecting, so learn where the arc actually reaches instead of flailing at close range.

Sweeping a group cuts the damage down hard, which is normal whip behavior and means this is not crowd control. Treat every swing as a single target call. The obvious partner is the Imp Staff, since the whip is already leaving its victims burning for the imps to build on.