for anyone not at max levels/rarity, this is often caused by being in a FP too high for their realistic capabilities. Demoting a bracket or two really does help. Nowadays there are occasionally some pretty robust players who have also dropped in FP for whatever reasons. So it won't completely eliminate maxed out lines, but it should significantly reduce the frequency. Expo absolutely can be impossible at low levels. There should be a turning point where enough investment in hero development will turn that tide. Pushing FP too high has always made it harder to get over that hill.
Also, that's not the tilt I was speaking of. I meant only the "line of scrimmage" being about 5-10% to the right of center in Expo. It is one of the modes where that effect is most noticeable. When Wolf was the end-all-be-all it had some tangible consequences. (still beatable) Far less significant with the "new & improved" KK.
I will retract some of my earlier statements about casualties however. You've reminded me of a time when intentional sacrifices were a key part of the overall strategy. I'm assuming the OP is not at that point in the difficulty curve, but for anyone who is, figuring out who and when to kill off is very important. One of my faves was Mega+Spike (and nothing else). I knew they weren't going to win, but Mega clumped everyone on the right edge where Spike could hit em all. I was expecting at least one of the opponents to take a crit and die. Breaking up their synergy was sometimes worth sacrificing (what I then considered) a couple mediocre heroes. That "hole" in the defense gave me a new angle to pry it open. The more "softeners" one can figure out, the more hurdles that can be overcome in a run.