Okay, let's compare the scenarios then. First scenario is the one you just described. Second is:
1) Drawing an Eternity early enough, drawing a Pulverizer early enough, hoping you get a Crusader from Rewinding a Skeleton. THREE dice rolls instead of 2. -OR-
2) Drawing a Pulverizer early enough, and drawing a Crusader early enough. 2 Dice Rolls for this one too. While this is a possibility...the damage potential provided by Fallen Druid is much greater than a single Crusader. Also, let's not forget that, as you said, by using this method you would be wanting to save Eternity until late game, no? In that case you would need to spend ~21 turns Rewinding creatures to get the same damage potential as a Fallen Druid and you would have to stop as soon as you came close to decking out. Druid can continue to be used even after this point and it usually needs to be used after this point; also, this generally means that your duels will take longer than they have already. For Rainbows running Elite Queens, this tactic will reduce possibilities greatly.
I wasn't talking about playing Eternity early, Druids tend to be useful late-game when you already have control of the field, same with Eternity on Skeletons. Crusader is already run in rainbow decks due to its ability to run with both Pulverizer and Eternity... it really doesn't matter which you endow, but in either case Druid is an extra card, which
could be replaced with the change to Skeletons. Here's what I originally said...
Rainbow decks no longer have to pack Fallen Druids to stack high amounts of damage. Now they can just use the trusty Eternity.
You seem to think I somehow said Druid has become obsolete, but I didn't. Eternity is now just an alternative form of increasing your damage potential. You said you like steal/destroy mutants, and I said I haven't found them very useful late-game, which is when mutations tend to happen, Pulverizer is much more useful and you can run both it and Eternity with a Crusader - many rainbow decks now do that. Sure, Eternity ends up with a dual purpose and can't continue expanding your army while avoiding deckout, but I haven't found that to be a problem either.