Worth noting that the green tile buff can also surpass Tarlak’s cap. Heimdal + Tarlak + Ratatoskr can result in very deadly green matches.
What does make Ratatoskr tricky to use though is that he’ll only enhance the current green tiles on the board. The ones that follow later after his skill won’t be enhanced.
Basically, he rewards smart board manipulation, and I personally like that design as it is dependent on player skill to make the most of it. Worst case, he’s an average speed healer – best case, he’s a great support buffer and healer.