A few stealth changes have crept onto live servers in patch 5.4.2, without making it into the patch notes. Both of them relate to PvP, and while one is accidental and will be fixed it could be coming in 6.0, the other is here to stay. If you're an arena-focused hunter, you're not going to like this much.
First up, let's examine the change made to Dampening. Dampening was introduced to the game after patch 5.4 to fix the issues caused by The Crowd Chose You. Dampening is a stacking healing reduction debuff, that decreases healing done to players and pets by 1% per 10 seconds, up to a maximum of 60%. This would usually kick in after 10 minutes, but was starting at 5 minutes. This was accidental and will be hotfixed as Community Manager Lore explains:
No need for alarm – we'll be hotfixing Dampening back to a 10-minute start time (with Arena matches ending at 20 minutes).
As you might be aware, the WoW Arena Invitational at BlizzCon was configured to have Dampening begin at 5 minutes, with a 15-minute round timer. Those changes were intended solely for BlizzCon, but made it over to live servers as part of the 5.4.2 patch. Again, this was unintentional, and we'll be hotfixing things back to normal ASAP.
However, the change to hunters' Dismiss Pet is intentional. It was being used to get full-health pets in the arena, and to reset cooldowns on things like Roar of Sacrifice. Now, hunters will only be able to swap pets before the arena starts, and this is intentional. It won't be changed back. Hit the break for Lore's post on the matter.