Haste does not improve RPPM proc chances since this tier.
Even on the same bosses it's really just up to who gets better procs on a pull etc single target or multi-dot. Just kinda the nature of things when (using simcraft as an example) your dps range from min to max is 120k+. Shit gets kinda silly.
Sorry if this was worded confusingly or something, people reading text and all. Simcraft has over valued haste SINCE rppm came into play, NOW it overvalues haste even worse BECAUSE of BINDINGS. The latter *does not* include the former.
Hopefully that's a little clearer.
Stop guessing and post something that actually makes sense.
Pretty much this.
As I've already mentioned I simmed my toon for a 450s (+0-20%) fight against 1, 2 and then 3 boss mobs with the following reforge setups:
1. Mastery + 9778 haste BP
2. Mastery + 12k haste BP
3. Mastery + 13.7k haste BP
4. Max. haste (~50% haste raid buffed)
I'll make it short: Surprisingly for all 3 situations the 13.7k haste BP was the strongest, not the always recommended 9778BP. That on was actually far behind, by almost ~15k dps on a 3 target fight. 2nd rank goes to the max haste build.
I think according to these results it's safe to say, that the 9778BP might not be the one an only BP to aim for, but the 13.7k BP, provided your gear is good enough. I might even go this far and say that it might be worth sacrificing mastery for haste to reach the 13.7k in low ilvl gear.
But after that BP the dps you gain from 1 haste gets extremely low and haste itself devalued by a lot and one should start stacking mastery like there's no tomorrow.
edit: If you're interested I can link the results.