I don't know the answer, but why would you want to fight against bots?
It looks like the goal is to level the filler chars, so probably because they are easier to defeat than meta teams. Not sure if you need to win versus humans for the PVP rewards or not, so maybe that would be a cheeky way to do them as well.
Since a few weeks I also could no longer get a bot with 4 30s and 2 low levels mercs. Eventually after 5min I was always matched with a real person, almost always one with some maxed f2p mercs (usually Xyrella, Samuro, Cariel as opener) and some non-max sub-optimal overall comp. I felt kind of bad beating these people so now I no longer queue such comps