I feel like all this guy needed was for the 9 spawn to not be conditional on lethal damage.
The problem is even if you get your good setup, it is highly unlikely that you hit 100% devour chance, especially without leaving extra turns on the board. But missing the devour just stalls you completely - not only do you not have any mana, but you also gave up a board that likely has a bunch of 4+ matches on it and when you get your turn back it makes it an uphill battle to even be able to cast again. This means even if you have good setups with him, if you can’t get to 21-25 red gems on the board for the guarantee, he will ultimately be self defeating often in what should be a good setup enough to make me not want to use him at all. For setups where I don’t just sit there and loop trying to get to as many reds as possible and just use spawners and storms because I don’t want the fight to take forever, I generally average around 13-18 in reds on board, for around 60-80% devour chance with the burns. I can sometimes chain this into devouring the entire team, but if I fail one devour I’m scraping trying to get my mana and board state back for longer than any competent team would take to clear two full matches. The same is true if I completely brick a spawner cast, as it is for most spawners, but I feel this an acceptable risk if he just spawned all the time - I still counter it in the same way, since it is basically harmless with few or no reds on the board, and my win condition and setups are still the same, only I don’t have an unacceptably high chance to take one on the chin when casting in a situation that should be favorable for me.
The alternative would be for him to not do completely terrible spell damage (at least 3x what he does now) so I could target weakened enemies and either devour/get bigger or get a guaranteed lethal with guaranteed spawn, or then take a calculated risk on a bigger target if I have closer to a guaranteed devour. Or he’d be flat out “good” with a x6 boost ratio. Either of those would secure him as remaining a “momentum” based troop without it being too much of a dice roll that it is now.