The original phrasing wasn't ideal, I have to say. When I read "Elites at the highest tier", my first thought was "You mean reds? Maybe the gold as well?" But when I followed the link I realized the challenge had graded versions.

: Had a couple minutes last night and actually killing the remaining elites did
: not make it much easier.

Sounds like the other covies were really annoyed with you then. But with the Elites gone, I'm surprised you couldn't just run past them. Especially if you had full health. Not sure exactly where you were though.