Just did some calculations and found the right numbers, at least according to my character.
I believe that Combustion only benefits from Torch and Burning Instinct. (And an extra bug)
So the numbers on my Combustion are:
- No Torch and No B.I. = 60
- Yes Torch and No B.I. = 118.9
- No Torch and Yes B.I. = 82.5
- Yes Torch and Yes B.I. = 194.3 (bugged)
If we add the values of Torch (bonus 58.9) and B.I. (bonus 22.5) when they are alone, we get 81.4 . Which is very far from the bonus of 134.3 that we have when both are active.
The difference is 134.3 - 81.4 = 52.9 . This extra value comes from the B.I. node being applied to the Torch Glyph… So if B.I. multiplies the burning damage by 0.9 and we get the Torch bonus of 58.9 and put then together we have 58.9 * 0.9 = 53.01.
The difference between 53.01 and 52.9 is because the Torch bonus is rounded up on the tooltip, in my calculator it match perfectly.
In other words, the combination of Torch and B.I. is double dipping with Combustion. (I assume it is a bug)