You're flat out lying. They did slow the game play down. You're telling me, that when someone brings out a bubble shield, you can still kill them in the same amount of time as in regular combat? No, unless you're close up, in which case it's bs because they now can bring you to one shot from a melee or they can stick you and you both end up dying. That's frustrating for the player who should have gotten the kill the same way an AL user alters the fight. A slight invulnerability can change the outcome of a kill easily. That is why when you're one shot, they encourage you to hide behind something in MLG. It gives you extra time to live and possibly be saved by your teammates.
Also, it did not take a couple of seconds to activate a regen. It happened in a second, and it would drastically shift the favor onto the regen user. In any case, the player will live longer most times and thus it slows the gameplay down, and buys the regen user time to stay alive just like the AL.
Also, CQB made it a random melee fight. Most users would use it at mid range anyways when they had a BR. I also noticed, you're arguing that the needler will save you. Right, except the weapon sucked so why would you use it in the first place? You're also underestimating the intelligence of players using the regen. In higher levels, they wouldn't just activate them in the way you're saying (CQB), so those CQB power weapons don't matter in this discussion.