I'm not saying it's just you, but many people run and face those teams and are not running into this issue.
Which is why I suggested looking at remodding toons and looking at a different focus for more power.
I dont have a chance to annihilate more than 3 toons and the 3rd is usually just because he gets to that ability in the time allotted. My normal is 2, then hit auto on the last one and see what happens.
You may also want to consider you kill order and damage focus. In this current meta that can play alot into the battle.