Given how very, very useful Mutation is in this deck, I'm surprised you're not using Fallen Elf instead of the Mutation spell. Druidic Staff doesn't seem like it would be very useful in a deck like this, so you don't need to worry about straining
.
May I suggest -2 Mummy, +2 Flesh Spider, and throw in a Wings or two somewhere in there? You have no shield, and wings+spiders can completely shut down some decks. Of course, with the large
usage, you won't be able to afford using Toadfish's effect... Alternatively, if you don't like Wings, Arsenic would still be a better card than Mummy or Druidic Staff.
-Hematite Golem +Graboid. Even with the use of strained
, Graboid should still be considered. It's just too good not to be.
Gravity Pull + Toadfish + Mutation really isn't enough CC, especially as you WILL use Mutation on your own creatures. If you don't go with Wings/Spiders, you can replace Phase Spiders with Lightnings. Those things can take down almost anything. Another good substitution would bee Quintessence; you don't want to lose that Steal mutant, that 17/2 Crimson Dragon with Dive, or that Fallen Elf (if you have one).