First of all, I want to thank you for a nice and simple tools you made.
Secondly, there are few suggestion that you can made in order to improve this sheet.
Actually, it's not that difficult to precise impact of +hit on dps.
1. Change time spent casting for COA, UA, Corruption, SL, Immolate and SB.
TimeSpentCasting = NumberOfCast / ( 0.83 + Hit )
2. Haunt.
There are 2 major impacts of Haunt's misses: lossing 20% of dots damage and necessity to reapply Corruption.
In case of not 100% of hit, Haunt up time will be equal your hit chance and Haunt multiplier to dot's damage will be:
HauntMultiplier = 1.20 * ( 0.83 + Hit )
Keeping in mind that we have to reapply Corruption 2 times for every 3 Haunt misses, Corruption's number of casts will be
CorruptionNumberOfCasts = 1 + HauntNumberOfCasts * ( 0.17 - Hit ) * 10 / 15
3. Soul Siphon is different. As we only loose GCD per every SS miss ans it's channeled spell, the best way, imho, to increase casting time for each spell on actual GCD fraction
[code] SoulSiphonCastingTime = 15 * ( 1 - Haste ) + Max( 1, ( 1.5 * ( 1 - Haste ) ) ) * (0.17 - Hit)
4. Also, please change Formula for # of NightFall procs. It must be C9 / 3 * 0.008 instead of 200 * 0.08