I think Greg will only become important once we dispatch with Cora. And I keep going back and forth on when that will happen, before the end of the season or at the very end of the season.
Yep, I’ll be surprised if Cora outlives this season, and I reckon they’re introducing Greg to be a major force for next season. They’ll probably drop some really big bombshell to do with him in the season finale, and leave us to agonise over it for the whole hiatus. They’re gradually weaving him into the story, and I believe it’s building up to something huge.