There's many, many things that could be inflating your DPS.
  • Are you sure your model is using the proper rotation?
  • Are you using the correct formulas?
  • Are you clipping your models DoTs correctly?
  • How are you distributing your buffs in your model? If you're not averaging them out like I am, are you sure these buffs which are applied to your DoTs are also being clipped properly?
  • Are you making sure there isn't an error in the stats you've inputed?

I never calculated DPS first. I always make sure to calculate PPS, THEN add that into the damage formula. The PPS takes into consideration all buffs, crit, skillspeed, battle litany, everything. This PPS is then plugged into the damage formula.

Then, there's also this question, how are you adding AAs?

My Model will always calculate expected DPS to be 10-20DPS lower than in-game as all of my buffs and DoT ticks are averaged out, rather than being used on specific skills along with other, really weird stuff I cannot explain.