Marvel Puzzle Quest players use “tanking” to mean “intentionally losing matches” rather than “absorbing damage.” This is a method of manipulating the matchmaking algorithm, and it is reportedly quite effective.
The idea is this: if you win 95% of the time, you will be grouped with other players who win 95% of the time. It is easy to win almost every match because you can “skip” in PvP after seeing the opposing team, so you do not start matches you know you will lose. If you do that enough, you start seeing level 100 opponents in your first few weeks, at which point you can skip all you like without finding a good fight. So every now and again, you need to lose a tournament intentionally, just keep challenging and losing, and then your next few tournament groupings will be much easier. Otherwise, you will not make it into the top 10% of your tourney grouping to get the new heroes you need to have a chance against those harder opponents.
This is an unfortunate mechanic. We want matchmaking systems to provide evenly matched opponents, but the asynchronous PvP system that Marvel Puzzle Quest uses seems to encourage guaranteed victories until you hit a wall of very likely losses. Neither end of that pendulum is good game balance.