Seems punishing for people who queue solo for Frontlines in particular. You can be the best player in the world, but be unable to get first place in a match because you either get a poor team, or your team is decent but one of the others teams is better in every way. Having no rewards for an average of 66.6% of your tries MINIMUM is the fastest way to kill any interest in a mode for most people.
There's already rewards you can go for that only count wins.