Currently, among the longest contract, we have an exclusive ''Complete 12 contract using a vanguard character''.
Now, using vanguard or heavy character for contracts is boring. Nothing else but long and boring. My suggestion is to expand this contract to either make it generic (Complete 12 fights), reducing the number of fights or, my favourite pick, expand the contract to randomly rotate between Vanguards, Heavies, Hybrids and assassins.
Really... Using the same characters over and over is just boring, and if we take in account that we have only 4 vanguards and heavies contrary to the 7 assassins and hybrids... yeah. I think people get it.