I don't think you should really care if another job outperforms your main when every job can still clear all content in the game without a problem.
Are you having fun? Yes? Good. Just keep playing your job you have fun with.
Should BLM be doing more damage? Yes, I agree. But if I mained BLM I don't think I'd drop it just because another job currently out-damages it. If people are excluding you from parties because you play BLM instead of PCT then their party wasn't worth joining to begin with