In my opinion, there were several things working against it:

1) The core combat system just wasn't fun. And since you spend a majority of your time fighting in a MMO, that's bad. I'm not why exactly it felt so bland and boring. Maybe a lack of meaningful options for each class in any given situation? Maybe the 1.5 second global cooldown on every skill in the game? Maybe the pacing? Whatever reason, it was just unexciting. Maybe I was spoiled by Guild Wars.

2) Takes too long to find the instanced PvP 'scenario' matches. The 'open RvR' was very hit-or-miss. I'm not a huge fan of PvE, so this was a killer blow for me.

3) Takes too long to level up. This probably wouldn't be as big a deal if it weren't for #1 and #2 on my list. If the combat itself isn't fun, and the PvP isn't fun, then the only other appeal for me in games like this is trying out different builds and experimenting with stuff. Doesn't work so well when it takes forever to level.

Don't feel bad though, a friend of mine who is a huge Warhammer fan (he's got hundreds of figurines, used to compete in Warhammer tournaments, etc) quit after a few weeks of playing. And it looks like we're not the only ones. Check out the declining numbers over on XFIRE. Sure, it's not scientific, but shows a pretty steady decline in the # of hours played and that's not a good sign.