It's like the X-Wing, it can be made to handle several roles but is not the best at any and that's why it is skipped so much. It's a super balanced ship and has no glaring weakness. The problem in its original form was more pilot abilities then it was anything else. If the scum Boba had been an imperial he would have seen plenty of play times in the early waves, Kath probably would have been seen more too.
Well to say it has no weakness is an understatement. It does have a weakness and that is getting flanked on its sides by more maneuverable fighters. Now granted almost all ships have that weakness as only a few have turrets or high pilot skill + repositioning but the firespray's large base I find tends to magnify that a bit more.