Asheras made some good points, none of which I'd disagree with.
I would argue that the humble Artificer, the whipping bitch of p2p classes, is a good call, especially for Warforged PLs.
Trap XP, and OP abilities for Heroics, plus a dog to pull levers. INT to damage/ Attack with buffs or splashing in the Harper tree, and provides a shit-load of Skill Points and buffs the Repair skill for boosted Reconstruct. Self Heals even better than Wiz or Sorc on a Warforged.
UMD is a class skill, which all by itself is worth the price of admission.
Almost seamless multi-class with Rogue, which would net you evasion for a 2 level splash.
They suck donkey balls in Epic, but if you're just grinding on the Racial PL Hamster wheel, it's all "20 and TR" anyway.
You could also argue the reverse in Pure Rogue or Rogue 18/ 2 Arty, for Rune Arms and the dog to pull levers. Gets you improved evasion and all kinds of sneak attack damage, plus some traps for shits and giggles.
Warlock of course, just blasts through everything. You won't spend enough time at low levels anyway for the slow start to matter. You can have Chain Blast at level 2 if you're stingy with AP.
Then stock up on some Spell Power pots from House K (or where-ever) to cover the difference in DPS.