Basic Strategy Question: How to deal with assist attacks

Stun the attacker who has the ability to proc an assist. I'm looking at Aayla here, who can stun as well as stun on counter. Counter in itself is another ability that can at least mitigate the effect of assists.

In the case of B2, my personal thought is you are best off keeping him locked down until you're in a position to deal with him. If you can't control the opponent with at least a degree of reliability, you risk being overwhelmed.