Please dont... I get the idea behind it and also the frustration there, but first off: This is the first week for this mode, people are still learning.

And second... I feel that all those PvP-mounts should be rewards for good playing - yes, I realize that there are 23 annoying adds on your side, trying to hurt you just as much as the 24 people you want to kill. But those achievments are an incentive for potentially everyone to give their best and win. You can also try to influence those 23 adds by giving orders - sometimes they'll follow, sometimes they dont, thats true. But I've seen matches turned around and won after one person spoke up and took the leading position.
We've had so many problems with people afking for exp, because wether or not you won the game didnt matter. We dont need more people afking to get those mounts.

And third: This is the first week of this content and maybe you're unlucky with groups right now, but thats gonna change. Once you're lucky - once you're not. Your proposed change would make it actually harder to eventually get the mount. You dont really believe yourself that 1.000 (or even 500) matches are more likely to be reached than 100 wins, do you?