i have played a wizzy myself to almost 30 and it is indeed easymode for the game, provided of course you choose the right mobs and right gear. its not uncommon for me to level twice in 2 hours solo on solo content a couple levels above me outside, not in an instance. that said, i am currently working up a warlock and am currently at lvl 24 and i can say without a doubt that they both are just as easy, for different reasons. warlock gear: i choose the same as the wizzy... +sta/+int armor and jewelery. i do not go totally +int, because you loose only 12 int with this setup, and GAIN 28 sta. this gives you nearly as much hp as power, and let me tell you, when you solo alot on either of these classes, it makes a HUGE difference, believe me. warlock mobs vs wizzy mobs: warlock mobs, you want to find lots of linked solo mobs for fastest leveling solo. the heroics are just too tough unless they are green to you. for wizzys, you want to find lots of single mob solo mobs for fastest solo leveling. both of these types of encounters should level you equally fast given similar spell levels and similar gear. you get less xp per mob in linked encounters than you do from a single mob encounter, but you burn more power burning down the linked mobs for more down time from time to time, so given the right food on both, the wizzy will have far less downtime than the warlock, so xp should even out a bit over time. with the +sta/+int gear on both, and magi shielding AA enhancement maxed out from EoF, i can take quite a beating, and i find that just tanking the encounters works well, and keeps melee and defensive skills at max for the level. the ward usually lasts long enough that i get dropped down to around 60% hp , no less, and that can make a big difference, because with the right food and drink, i am usually near full hp/power by the time i have sized up and pulled my next encounter. that aa alone makes all the difference imo when maxed out early.
Keep in mind that wizard is far inferior to warlock all the way to level 50. This is because warlock has the exact same single target as wiz but better AoE. You really cant judge wizard until you get Ice comet, plain and simple. They mine as well rename the class Icenova'er.
