Except there is no map issue.
You have one faction getting massacred in WPvP? People lose faith in their faction.
You lose BGs outside of premades? People then flock to premades when they are interested in trying hard to win.
What you’re left with is people who aren’t interested in trying hard from start to finish in AV, because if winning is what they’re interested in then there are much more convenient alternatives in other BGs. So you’re left with the casual “whatever happens will happen” crowd, who gives up at the slightest sign of trouble.
So because you can’t do premade exploits in AV as easily anymore, of course you get the “winners” flocking to other BGs.
Widespread mindset issues have been the problem plaguing the Alliance side ever since the WPvP chaos pre-BGs.