Ask and ye shall receive. Napkin math CS vs HotR using presently understood values.
At how many targets does CS equal HotR?
CS: (633
* + Weapon Damage + (AP/14 * 3.3)) * 125% * 110% (Sword of Light) * 104% (Judgements of the Bold) * 67.9% (fully debuffed Armour mitigation) * 1.x% Mastery
CS: (633 + Weapon + (AP/14 * 3.3)) * 97.1% * 1.x% Mastery
Let's pretend we're using a 3.3 weapon speed. Yes, this is a lie, but it simplifies the calculations. CS is normalized to 3.3, while HotR should use true speed (3.6 across the board at the moment).
HotR Base: (Weapon Damage + (AP/14 * 3.3)) * 20% * 110% (Sword of Light) * 104% (Judgements of the Bold) * 67.9% (filly debuffed Armour mitigation) * 1.x% Mastery
HotR Base: (Weapon + (AP/14 * 3.3)) * 15.5% * 1.x% Mastery
HotR Splash: (Weapon Damage + (AP/14 * 3.3)) * 35% * 105% (CoE) * 130% (Inquisition) * 1.x% Mastery * Targets
HotR Splash: (Weapon + (AP/14 * 3.3)) * 47.8% * 1.x% Mastery * Targets
We'll call (Weapon + (AP/14 * 3.3)) "Mod Weap" just to shorten it.
Balance point would be where CS = HotR base + (Splash * targets).
Balance: (633 + Mod Weap) * 97.1% * 1.x% Mastery = (Mod Weap * 15.5% * 1.x% Mastery) + (Mod Weap * 47.8% * 1.x% Mastery * Targets)
First thing to notice - both sides have identical 1.x% Mastery multiplier. The value of Mastery is inconsequential, the ratio between the abilities remains identical. Divide this out and it drops cleanly.
Balance: (633 + Mod Weap) * 97.1% = (Mod Weap * 15.5%) + (Mod Weap * 47.8% * Targets)
Balance: 614 + .971Mod Weap = .155Mod Weap + (.478Mod Weap * Targets)
Balance: 614 + .816Mod Weap = .478Mod Weap * Targets
Balance: (614/.478ModWeap) + 1.71 = Targets
That 614 damage divided by 1/2 your modified weapon DPS is an ugly value, but we can deal with this.
So we need somewhat more than 1.71 targets. X is modified weapon damage. 614/X needs to be 0.3 or greater to require more than 2 targets. Thus .3X = 614, or X <= 2047. We would need
less than 2047 modified weapon damage to require more than 2 targets.
As long as modified weapon damage is greater than 2047, you can swap to HotR at 2 targets. Hint: questing greens and a
large club should be well over 2047 damage.
Also recall we pretended we had a 3.3 speed weapon. At 3.6 speed, HotR gains a bit more.
Bottom Line: HotR should be an increase on 2 targets at every level of MoP gear.
* - wait, what's this 633? 633 * 125% = 791. It's cleaner math if we move it in with weapon damage. Lets us combine our multipliers.