I'm finding the real big skill hurdle is movement. This isn't a stand-still game, even when you are doing solo PVE. Pretty much every weapon/profession combo has both close and longer range skills, and everything can be used while moving. So learn to move. For some professions, that's just mostly going to be dodging away than moving back in. For others, like Elementalist, it should be a nonstop thing unless you are using a close range weapon like the dagger.
Very often I catch myself lapsing into traditional MMO style and just standing there, taking the beating, when there's no good reason I should.
In other news, I'm not sure Mesmer is the right pick for me. I think I'd enjoy it a lot in PVP, but the PVE is kinda boring. With a scepter, you get clones by auto-attacking, so the mob almost certainly won't attack you. Unless it has an aoe skill, you'll put them up faster than they can tear them down (you get 1 clone every 3rd auto-attack). If they do come at you, you can block any unavoidable attack using your second skill, which creates a clone to intercept it. Does a lot of damage too. Last skill causes confusion. Not the most powerful (confusion causes damage each time your opponent uses a skill), but when combined with the fact that those skills are going to hit an object that isn't there, it's decent.
Using a sword is more fun, you put out a ton of damage, but don't get anything close to the same clone support. Your auto attack debilitates your foe (stacking defense debuff), rather than creating a clone, so the mob is actually going to be targeting you. You do a lot of damage though. Your second skill does damage while causing you to evade all attacks for 2 seconds, which is nice. The last skill creates a clone on your target, which you can switch places with at any time. Nice way to dodge away from an attack then get right back on the mob. All in all, it takes more skill. I've died more, but had more fun since I started using it.
I haven't tried using a staff yet, but it seems like it's heavily skewed towards grouping. Mostly AoE and boon/condition stuff. Same for greatsword. It's AoE and support stuff, but with a much stronger skew towards dealing damage. Sword almost certainly does better single target dps.
Focus gives you two support skills, a crippling field to snare attackers/speed you, and a defensive phantasm to block projectiles. It looks like PVP stuff to me, but it could be useful if you're fighting multiple mobs with a scepter I suppose. Use the phantasm to block ranged attackers while you kite the melee.
Pistol is kinda meh for PVE, imo. The duelist phantasm just doesn't do enough damage, and the survivability skills of other secondaries are better than Magic Bullet, which hits 3 targets and gives one status to each (stun, blind, and daze). Daze is by far the strongest status, imo, but it only hits the 3rd target (so you don't get it if you are only fighting two mobs--3 is unlikely, in my experience, outside of group stuff).
I haven't tried dual swords but I want to. Secondary sword adds a clone skill and a sword-using phantasm. Should help make up for the weakness of the sword with regards to putting up illusions.
Torch is quite strong. You get an invisibility and a mage phantasm. The invisibility blinds foes when you activate it and burns foes when it wears. The Mage grants retaliation (damage reflect) and confuses targets.
If you use Scepter/Torch, you simply should not die. Ever. And your enemies will kill themselves as they attack illusions while you pepper them with attacks. Not super fast, but not slow and ridiculously safe. If anything ever does go for you, you use your invisibility to blind them and get away so your clones can get them back. Sword/Torch is still strong, but not as much so. That's mostly for the oh-sh*t button, since confusion isn't nearly as good without the ability to spam illusions.
Not a bad class by any means, whatsoever. It's boring me because it's too easy, and there's only one other interesting solo weapon.
My biggest complaint? THEY CAN'T USE DAGGERS. I mean come on, the harlequin juggling daggers is an iconic image and I want it!
Not abandoning him, but I don't think I'm going to focus on the mesmer until I start trying PVP stuff.
It'll be close, but Romney has the momentum.