The arena community has been asking for this for awhile, and if you want to know their reasoning, Serennia discussed it just the other day. I strongly suggest giving it a read. Replenishment is a game changer in the arena, and in a format with teams so small, you can't really expect every team to find a Replenishment to slot like you can in 10 and 25 man raids. Replenishment essentially being a requirement in the 3v3 format would be a disaster, and it's been made pretty clear that teams with a Replenishment have a severe advantage over those that don't.
A post-Patch 3.1 world seems to be one where broken things get fixed quickly, rather than just sit there broken for months until the next content patch. As long as that holds up for more than these few weeks immediately after the patch, I'm a fan of it.