Well I don't quite agree with you.
I think Pandaren are a fine race, but it is the idea of neutrality itself which failed.
Sadly this undermines the Pandaren. When I try and play one it alone out of all the races in the game does not feel right. As if it doesn't belong. At first I thought it was because some people had a point, that the Pandaren just aren't really a Horde race.
But when I tried an Alliance Pandaren I found that the same feeling of rootlessness, of not belonging, followed me.
Neutrality definitely hurt the Pandaren, and has prevented them developing a strong narrative within the factions. There is no point in compounding that mistake by adding another neutral race.