Who plays with which heroes in the Inferno faction?

It simply doesn't make sense to point out the advantages of certain heroes in that it's easier for them to acquire Special Abilities (you yourself pointed out Grok). On a large map, any hero is suitable for this purpose with a mentor.

They are suitable, but Grok already starts with good skills, while others still need to acquire them. And some heroes cannot acquire Special Abilities without a mentor, so you will have to invest money. And there is no guarantee that other heroes will get the necessary skills. Therefore, Grok is the best option, and the specialization is good for large maps.