Mm.. let's see.. Neo-USEM has no CC bait, so Frogs will be CC'd when they're played right off the bat. I don't think 6 copies of Mitosis are necessary or optimal. Another downside is costing 4 when upped.. this'd be an auxiliary card in USEM much like a Dragon would be.
Something with 3 Cocks and 3 Mitosis would be smarter against these Elders if you only consider winrate, or even 4 Cocks/2 Mitosis. It doesn't make much of an impact though, because the two main problems are these:
Shield lockdown with Wings, Dim Shield and Hope.
Excessive CC, such as Pandemonium, Maxwell's Demon, Shockwave, Lightning and Rage Potion/Red Nymph (AI is too dumb with Oty).
Adding Mitosis solves neither and slows the deck down. With less speed, you'll be -even- more likely to let the Elders get set up. Conclusion: with 4 cost, it's not practical for speed at all.
Upsides: late-game when you often have tons of
, a Mitosis will be more useful than yet another cockatrice. Often you'll find you're doing enough damage to finish in two or three turns, at which point adding more doesn't help. With Mitosis, you could ramp that damage up faster and maybe shave a turn off in some cases.