I've flown two matches with a flamethrower-gat build against BFS with a SIR-Ryder team tonight.
Based on these experiences I think the flamer is in a acceptable state on a competitive level. It lacks the raw killing power of competing builds which is usually necessary for brawly builds against experienced and coordinates pilots and crews. Still I think it might be an interesting option for a couple of builds (side weapons of goldies, 3rd weapon for trifectas, squids, etc).