The problem is, it should be possible to position new ships so that they can compete with alternatives rather than being overwhelmingly better or worse.
Let's face it, even if they cut & pasted the FdL's stat's directly onto the Mamba, the FdL would still have an advantage, simply as a result of the Mamba being much bigger and, thus, being a bigger target.
They've given the Mamba higher speed, which could arguably balance against it being a bigger target, but then they've also given it wacko heat-issues, weaker shields and less agility too.
The end result is a ship that fails to compete with the FdL in any meaningful way - even if it is a pretty nice ship to fly (short distances) in it's own right.
Maybe we just have to accept that there's somebody at FDev who's a rabid fan of certain ships and absolutely refuses to allow them to be usurped in any way?
The T-7?