1. Moar grindquest!
It's not any more of a grindquest than coming up with 1,500 coins to upgrade a card.
2. Why normally mutate if you can this!
Because a permanent mutant will cost +5 quanta to summon, and Fallen Elves/Druids or Mutation spells will still be useful in taking out your opponent's damage dealers. Also, you still need Fallen Elves/Druids to upgrade the useless spam coming from your Graveyard, because a 2/2 Elite Skeleton will do 0 damage against most upgraded shields.
3. Set cards are good enough!
If the set cards are good enough, then what's the point of this forum?
4. Mutants shouldn't be sure thing, that's why they are Entropy!
Then why is Abomination a card?
This sort of thing would enable Mono and Duo decks to be much more versatile and well-rounded, because you would have creatures that gave you critical abilities that your base element doesn't get from ordinary creatures. I think that makes the game rather more interesting, because currently most of the Mono decks are damage-spam because you can't really waste cards on the "extra" abilities in each element, because it has more of a tendency to screw you on the shuffle than to really help.
For example, Mono-Death is critically hampered by a lack of permanent control, and has pretty weak creature control, but if you replaced two ordinary Ivory Dragons with Bone Dragons with Steal/Destroy and Devour, you've suddenly got a nicely well-rounded deck that has a much better chance of being useful (if you can handle the 15 quanta it would cost to summon them).
Or if you're really into straight-up damage spamming, you could replace a Ruby Dragon with a Crimson Dragon with deja vu. Now you've got two dragons (one with a random ability that you probably can't use) for 15 Fire quanta, and they both have better damage/health than a normal Crimson Dragon.
The trick would be actually -getting- these things as permanent mutants, but that's where the randomness of Entropy comes in: slim chance to actually get a useful mutant, and a slim chance to actually keep it once you've got it.