I initially tried a necromancer when I first picked up the game and was disappointed. Disappointed in one major way, a way that I wouldn't expect a third (fourth?) generation MMO to fall for: lack of scaling. Pets don't scale except by level. Their damage output does not change no matter what stats you have. Pet control also kind of sucks; a lot of the times they simply don't engage (especially when swimming). It could do with a kind of mini-RTS interface to give you better, tighter control over your multitude of pets. At minimum give them a pet bar to command all pets to attack or follow or whatever (even if you can't control them individually). Similarly, the potential of a DoT-based build is weak. While you can try to stack DoT power (I forget what the stat is actually called), your efforts are completely in vain when more than two or three people are fighting the same mob, because bleed stacks cap too low and are shared across all combatants. I can get up to 11 stacks by myself if I focus on it; why not just build for power, where my contributions are always functional and don't just vanish into the ether because of an arbitrary cap?
The other big disappointment I had was that there just wasn't enough Stuff To Do in combat. I'd rather have 3ish abilities to cycle between needing to be pressed, a couple that are longer duration but longer cooldown that are important to press, and then a few really important cooldowns. From what I can tell so far, the only thing that even comes close to this for necromancers is a staff build, and even then I spend 50% of my time waiting on cooldowns. And guess what? I go dual daggers, press nothing and still do more damage than a staff in anything short of a WvW zerg.
I've considered trying other classes, but my issues with number of active abilities seems inherent to the game. I can see where this could be good game design, but it still just feels boring. I had way more to do even on my EQ1 ranger, where 70% of my damage came from autoattacks. Never mind how active playing a bard was, or any class in WoW.