I had the same gut reaction but… it isn’t really that bad. It looks bad on paper, but in practice, it needs to be set up (or get an absurd amount of luck) to really run the board. And there is a lot of counterplay (he is not stealthy, has no immunites, and a relatively high mana cost, severe weakness to freeze, is pure AoE so it takes forever to kill stuff with vs spell resistance and sumberge can just be immune to his damage). If you use tools to counter the counterplay (such as MQ for half mana, a troop or hero for cleanse or bless, something to dispel, an empowered to accelerate him further), you are reducing the efficacy of your setup.
I’ve found he works best with a starting green storm and passive explosion traits or talents, but he takes forever sometimes if you are putting everything into this setup, even when the enemy has no active counterplay and you get an amazing start.
One thing is he kinda gets around the “combo breaker” (spawn streak breaker) rule, where spawner matches will actively attempt to avoid aligning the more you cast in a certain round. He can cast, the system will actively shift gems so they don’t align, but then he has an extra turn so you can just swipe those gems and get the mana anyways. I’ve felt that this rule was kinda unnecessary in modern GoW to begin with, though. The majority of the setups I use win the first time I have board control and full mana on a key troop.
After using him for a while outside of the event with free enchants abound, I don’t think the combo of mass spawn and extra turn is “inherently broken” like mass explode and extra turn was (and honestly, even this isn’t that broken anymore). If they were to change anything about this troop, maybe the baseline gem creation is too high - ie., maybe he self loops too easily from the get. His initial cast if you don’t prime the board and don’t disease anybody can already be pretty spotty sometimes, but this gets removed once he connects a few and diseases 2-4 troops. Slightly shifting this consistency to need slightly more setup would remove the ability to use any counter-counterplay tools and still have this troop be able to chain more than a couple casts without being really lucky.