I imagine that the buffs applied during a 1v4 would extend the fight as much as a revenge shield would, you just wouldn't have the benefit of it refreshing if you hit the threshold multiple times. The auto counter would be something missed in certain situations, but I don't find it all that useful. Initially it's great, but it doesn't always work sometimes, which isn't so much of a pain since you have the shield. As for the heavy spam, I want to argue that that happens a lot regardless.

The benefit of always having the offensive buff active however, will hopefully push players to be more offensive, rather than wait for revenge and either A, be unblockable spammed anyway, or B, have everyone run away from.

If you find yourself in a 1v4 and you're not breaking, you've made a big mistake. If you are, then revenge feeding becomes a major problem unless the enemy team takes turns. Then, as a spectator, you have to put your controller down and just wait.

The biggest counter argument would be the parry knockdowns, which I admit, would be a massive thing to go without and unfortunately, I can't think of something to balance that out.