This aims more at the 2v2 mode than the 4v4 domination, but functions on both. Playing 2v2, killing your enemy, only to have your ally getting executed and then the enemy running down and managing to revive his buddy to max health and stamina really isn't healthy. I've been on both sides of it, and the one reviving always wins. Getting something along 30-40% health would be a lot better.
Don't let them revive? In Brawl, trying to revive is very punishable as there is no speed up. Domination has ways to make revives speedier and getting in a revive during group melee is a big help, though the other team should either aim for executes or watch the fallen if they don't want that to happen.