It's definitely something you play by ear. If you can't wait for a Chaser, or if there's an opportunity to flank them, take it. Many times I've downed an enemy mech simply by flanking them and attacking from behind both the mech and its escorts. I'm not going to say it's easy, but I'd hardly call it difficult. It's really just a matter of reading the map/enemy positions and finding the best way around it.

Sometimes however, the unpredictability of just rushing them not only works, but ruins any attempts at defensive formation. I don't however want to put this out there like a highly effective strategy that should be used anytime.