Kozilek Return is probably much better then new Dismember, first and therefore new "Dismember is only "-3/-3" which mean id doesn't kill goyfs most the time, (even without creature most tempo decks can easy make goyf 3/4 - sorcery, instant, land) for sure it's best actually answer against delver without paying life dismember hurts a lot specially vs Grixs or RUG which have bolts as reach factor.
I would took analysis with Kozilek Return as probably worth splash card, but after few lists I still concident that B/G splash is still best removal (not hate vs combo !) configuration. Deeds and Decay cover all important threads from current meta, which G/R can't answer preboard (enchantments and artifacts, for example MD blood Moon or Back to Basics, which happens in Merfolks (surprise ==') can be very nasty, similar to fast tempo equipment. Abrupt Decay answers Delver best since it's uncounterable, same to each other painful cards like mention upper. Black also gives best answer to Monastery Mentor - Dread of Night, but with Pernicious Deed MD it's probably not worth, PD cover those pesky tokens with Mentor as whole.
Eventually problem is with Combo - like always to B/G decks, I splash a little white for Gaddock to hardcast (and under 4 GSZ), but even with 6 discards it's still not best MU which I can face. I added additional Sphere or Resistance and 2 Memoricede (mostly for Sneak but still useful vs Storm). I found that most important is not to die before turn 3, if you miss early discard it's mostly game since Storm player will just discard yours or keep hand with bounce/removal for your turn 3 Gaddock which ended brainstorm -> kill.
Anyway G/R doesn't give more answers vs fast combo, Pyroblast helps to stops assamble combo, but doesn't stop combo itself which mean you will be just dead turn 2-3. I think G/b gives more angles to consider like discard + hatebears, instead of Hatebears and Pyroblasts..