Rage Quittas
How it should be handled:
DC'ing results in a 25k BP loss. If they DC from matches back-to-back it results in a 50k BP penalty per match on their rage quit streak. Their BP can't just be lowered to 0 but can actually fall in the negatives. So serious trolls will have quite some debt to pay off come time for them to level up a new character.
Based on how many games they DC from in a day, if they reach a certain quota they receive a temporary perk ban, in which all perks are temporarily locked and can't be used on any characters. The only perk that shows equipped is Toxicity:
But, in this case, the perk will actually hinder you somehow during the trial.
Or... an even simpler solution... after they DC enough times, labeled them as a 'bad sport' and only allow them to join lobbies with other bad sports. From there, they can all rage quit on each other as much as they like.