I was a SAM main until I went DRG because while I don't enjoy it as much, it brings so much to our group and I want to bring as much as I possibly can. I was told its fine if I want to be SAM but I felt that going DRG will help us out in the long run.
The problem in general is that NIN is flat out way too good not to bring and DRG boosts the damage of everyone in the raid, especially BRD/MCH because of Disembowel, so their raid utility is more desirable.
There will always be a Meta and that makes balancing quite an issue.