I've been posting a lot about this potential change, since Senior PvP Designer Brian Holinka tweeted about it a while back when changes went in by accident after BlizzCon. And while I am still not a fan of the change, I can agree with it way more in 2v2 than in 3v3 or 5v5.
Why is that? Well, in 2v2, especially in healer-DPS versus healer-DPS, matches can go on longer, and even result in draws far more often than in the other sizes. Simply, a healer is not designed to be easily killable by a single DPS. As a result, it's harder work to take them down in 2v2. I won't pretend that I like the Dampening system, but it's better at 5 minutes in 2v2 for (hopefully) just one season.
What we don't know yet is just how far it will go.
Will this 5 minute change mean that Dampening builds up until the same percentage starting at 5 minutes, or will it just keep stacking higher until the match ends? Right now, it stops at around 60% at the match end, so will it just keep on going up to around 90% with it starting at five minutes? Or will it cap at 60% and just be there for 5 minutes? On a purely personal level, I hope it doesn't keep stacking up. 90% reduced healing will feel terrible as a healer, not to mention the other issues.
But matches do need to end, and if 60% isn't doing it right now I can see why the devs would let it keep stacking. I'd love to see some statistics to support whatever decision they do take -- greater transparency on the motivation for dev choices makes for happier players.
EDIT: Brian Holinka has clarified on Twitter that it will stack to around 90%.