Anything below 50 range for a TD is suicide because panthers exist
That's fair.
My reasoning was that it could handle the Panther better head-on. The pen bonus removes the 20% (or 27%) chance to bounce against the Panther, combined with better RoF, cuts down the frontal TTK from 40s to 29. The Panther's TTK vs Firefly is 23, so it would be an even match-up for cost.
Still, I know this idea is too late, and has issues.