I’d like to re-draw attention to @Razzagor 's idea, here.
Explode effect equals 50% Mana gain, and leaves any huge number/ storm summoning explode troops how they are.
Blast, Implode, Ka-Boom, or whatever you want to call it, can be used to help bolster the “non-offenders” back up to being useful, with the original 70% (or even 75) Mana generated.
I would keep troops that can explode rows and columns as “exploders”, and reserve the Imploder status for small number explode troops, like Golem, Ice Goblin, Gluttony, etc.
There would also be the issue if whether or not to reclassify some of the hero weapon’s explode a random/specific gem as Explode or Implode, based on the desired amount of preferred mana-generation; EX: Explode for Mountain Crushers perks, Implode for Spark Rocket perks.