I recently got Shale.
I thought great, a red Healer who cleanses ailments, so i quickly leveled him up… Only to find he is less than useless. I did 20 raids and he is too slow to cleanse ailments for all allies.
He needs to be 3* charge before his special is any real use. By that time you have had enough red tiles to kill the enemy without him.
Don’t waste your resources.