Both events are arguably avoidable.

Cometeor: If you let 5 or 6 casters of an opposing faction build up to battle high/fever, you deserve to get wiped. They earned those lb kills.

Double Teamed: from my experience 3 times out of 5, a team gets doubletapped because they positioned poorly, looking like easy kills for both the other GCs.

Whether you're getting doubleteamed or not, whenever you take direct damage, break range.. make them work hard for the kill.. They'll give up n switch to a different target if you make them work for it.