hmm, I don't see it. I played with the egg in zoo a bit and it was always strong. I don't find it that slow either because since I tended to not pop it myself and instead used it as a safety net to overextend into AoE more than I would otherwise be unwilling to do. I've never been a fan of the void terror combos.I think we're more likely seeing Egg cut from Zoo just to speed the deck up.
I actually wouldn't be too surprised at seeing Flame Imp cut too since there's enough upside 1cc minions to warrant skimping on a big downside one like Imp. Which may start pushing closer to non-Warlock Zoo variants.
As for non-warlock zoo, that seems really difficult to find a class benefit that helps the deck more than lifetap.