I've been flying the Mamba as my main ship and I'm going to call this out as nonsense. If the Mamba were "objectively worse than most combat ships" then the FDL that it was based on would not be the current apex of medium combat ships. The Mamba is not quite comparable to the FDL for combat but it is certainly a competitive alternative, especially for PVE. The poor turn rate is an issue but that's simply a tradeoff for the pure straight-line speed advantage and outstanding acceleration compared to other medium ships. The hardpoints are excellent, convergence is only an issue with fixed weapons and many ships have that issue so you can't judge it only on its suitability for fixed weapons. The Mamba's weapons all being dorsally mounted is actually a major advantage for sustained dps, especially in PVE combat, as you only need to keep the top side of your ship towards your enemy. Heat management is probably the Mamba's biggest weakness but since the Mamba shares the same size PP as the FDL there is generally a good power reserve allowing a good low emissions mods to offset this. Shields are actually good for a medium ship and you have plenty of utility slots for shield boosters, although there is admittedly limited room for SCBs.
Unless you're speaking specifically for PVP combat vs. an FDL you can't really call the Mamba "objectively worse than most combat ships" unless you are considering the FDL to be a sub-par combat ship as well.
