MMo's tend to be built like threadmills, if you stop for a while you'll eventually fall behind. And once you're behind you'll have to work even harder to catch up to others.
Mmo's aren't built with fair play in mind, they are usually made to reward those who spend more time, and if you split your time between mmo's you'll never get to the top of either.
Playing an FPS like PS2 is a fucking chore untill you get some weapons that are interesting, its the same reason i dont play much BF3 anymore, the grind to try out weapons is just too big. And once you got the stuff you want, you'll have to look for a group etc to hang with. They'll expect you to be active, to be able to count on you for raids or whatever.
At the moment i already have 4 arena teams, a raid team and an rbg team taking my time in wow. If i was to play GW2 i'd need a WvW guild and a PvE guild. Wildstar same deal.
I cant play a game half arsedly. Swtor being the only exception, as it was a enjoyable single player experience, i hit 50 and quit with no regrets, good leveling experience.