Currently still sitting on 1406 haste atm..
IIRC to hit the next tick for Immolate after 1406, is 2030 haste rating with 5% spell haste buff.
Assuming ISF's buff is cumulative and not multiplicative, 15% spell haste = 491 haste rating (rounded down from 491.8)
2030 - 491 = 1539
So I guess the new haste threshold to get the next tick of Immolate would be at 1539, counting the presence of a cumulative 15% buff from ISF and a 1.05 multiplier from spell haste buffs?
Correct me if i'm wrong. Positive comments would be appreciated.
EDITED:
Okay I just ran tests with an elemental shaman mate of mine who provided me with the 5% spell haste buff.
I can confirm the fact now that ISF is multiplicative.
At 1406 haste rating, with 5% spell haste buff and ISF, i was already getting 9 ticks of Immolate.
With the theory of ISF being multiplicative and the fact that 70% total spell haste is needed for the 9th Immolate tick,
Haste rating needed = 1.7 / 1.15 / 1.05 = 1.4079 (40.79%)
40.79% = 40.79 x 32.789 = 1337.46 (rounded to 1338 haste rating)
Tests on training dummies:
With 1338 haste rating, I was still getting 9 ticks of Immolate.
Removed an item with 27 haste and dropped to 1311 haste = only 8 ticks of Immolate.
Results:
Intervals between Immolate ticks = (1/1.7)*3 = 1.765s
Total Immolate duration = 1.765*9 = 15.88s