You can skip to the solutions on the bottom if you don't want to read the following explanation of the cards problems.
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The reason the card doesn't see play has nothing to do with the cost. It's the effect/pay off. The problem with the effect is as Swim stated the card wont's you to do two completely different things that contradict one another.
One it wants you to play a ton of spells. Easy enough. Then it wants you to flood the board with units. How do you do that? You can't have both. Its either one or the other.
At least that is what I thought till I made a deck that I have found can consistently do both and leave you with a full board of unites to buff up to anywhere between 7/7 - 11/11 by turn 7 or 8 and almost always have a mind meld in hand by then. By consistently I mean literally every time I played it. After 10 games with the deck I never once didn't have the mind meld and a full board by turn 7. I used all the multi unite spawning type spell cards between BW and P&Z with the usual P&Z board control spells and lots of BW an P&Z draw spells to find mind meld by turn 7 or 8.
The problem is mind meld is meant to be a finisher but it fails at its job. Up until turn 7 or 8 all you have are mostly low cost 1/1 chum blockers who you can't afford to block with most of the time. Then your reward for making it to turn 7 or 8 is to buff them all to 10/10 unites that all end up getting blocked then turn back into little 1/1 unites at the end of the round.
So you cleared the board but didn't even harm the enemy nexus 99% of the time. So unless you have another MM you are now dead in the water.
PS: I also tried using unites that spawned spells rather than spells that spawn unites but you rarely had a full board by the time MM was ready to be used.
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I'm sorry this took so long but I felt I had to first point out the problems before I could lay out the solutions.
Option 1: Make the effect stay. This would allow for you to clear their board, defend yourself during their turn, and hopefully finish them off on your next turn. It would also allow the enemy player time on their turn to take out some of your unites and build a defense for your next attack or do a board clear of their own.
Option 2: Give the unites Overwhelm or Elusive when under its effect. Though this maybe OP.
Option 3: Make the spell either burst or fast speed. This would allow you to attack in when you see a good opening where the enemy player can't block all your unites then when they confirm their blocks you hit them with MM and hopefully win.
