I'm level 44. The calculator is off by a lot at my level. Here's what I did:

My commander in AA+ 50/50 + lvl 100 friend in HH+ 50/50.
My guild has +4% in air/fire/water
Boss level 16 = 749/386, 14635 hp

So first thing I see is that when I take the guild bonuses away, the armor numbers are off by a bit. My health is correct however.

The calculator says I should've killed him easily with 21611 potential damage. 24k with crits. In reality I took the boss down to half in the first attempt. Then had to use up 5 more energy with the same group makeup to kill him.

Unfortunately I didn't record each attack made and his exact health since I'm at work and don't have the time to do it, but I can try again later with the level 17 boss.