I cannot level at al. I got one assassin stuck at level 4 (8000/8500 XP). I played about 20 lvl 1 missions to get influence until level 5 but not a single XP point. So I created a new character and play 1 mission on level 4 but I got 0 XP points.

I do have some pretty strong gear. perhaps this got something to do with it?

The rest of the update is awesome. 

Thanks

Power Level is increased by getting better gear with higher attack and defence on it. When you look at your power level bars you will see x/66 on each attack and defence. That means you need 66+ points in each to reach power level 2. Each item you have will have a Fist(Attack) or a Shield(Defence) to let you know. Item quality goes Yellow, Blue, Green and Purple in order from lowest to highest.

As far as account level goes, that will level like normal leveling once you reach level 20. So at 20 you'll be level 20 with account level 1. Next level will be Level 20 with account level 2 and so on.

Hope that helps.