I'm not 100% on this idea, so I thought I'd throw it out there to get some more opinions! To know if this is something people see as a problem or just part of the game.
Basically, sometimes I end up facing down a team in the gauntlet that is full of creatures that are either good with healing, very defensive, their only selling point is the “only allies attack” special, or energy regenerators. My team (while not all pack-mentalities and assailants, still averaging fairly good damage) can and will whittle down those teams over time, but not necessarily within the 20 rounds provided, and I could lose. The thing that bothers me isn't that I'll probably lose though, because that happens, but that I'm losing to a team that could never win itself. Such an enemy team, against almost any other team of the same level, would never actually win by eliminating everyone else short of a ton of critical strikes (if even), and under arena rules would be losing on time on almost every battle. These highly defensive teams are less of an opponent and more of an obstacle, and “defeat” your team only because their win condition (survive to round 21) is different from yours (defeat each companion on the team), and they would likely never fulfill your win condition of defeating everyone on the opposite team without a highly improbable streak of critical strikes, dodges, and much more than 20 rounds.
I guess I'm asking that whatever generates gauntlet teams detects teams like these and doesn't make you fight them, although other gauntlet improvement suggestions (like the one about seeing the silhouettes beforehand, so I know if my team will just be chipping at a brick wall) might solve or alleviate this issue as well. On the other hand, the gauntlet is about risk and maybe these uneven (in terms of end goals) fights are just something to account for in the player's team-building, so if the average player isn't more frustrated by these brick wall teams than the regular fighters that take down your team the normal way, then this isn't an issue.
edit: The reply below this one has some good ideas that would probably easier to carry out (much more of a concrete if-then) than having to detect if a team is too defensive or not before the battle. If you also have solution ideas, please share them!