"Combat ships" are not defined by the amount of utility slots they have. You're leaving out the Alliance mediums, and the Python is a perfectly capable combat ship, as is the new Corsair.Most combat ships (ships designed for combat) have 8 or 6 slots. A small portion of warships have 4 slots: FAS, Vulture, etc. If a person hunts pirates on a non combat ship (Mandalay, Python1, Corsair) it is his own fault and there should be no claims.
The ships that have 6 slots are solely the FDL and it's side-clones in the Mamba & Python mk.2. (And the Beluga, but I'll give you the benefit of the doubt in including that as a combat ship.)
The ships with 8 slots are the most expensive L-pad ships, that is, the "big 3" Anaconda + Corvette + Cutter, plus the Type 10 Defender.
All three of the "big 3" are multirole, with varying strengths and capabilities and limitations. The Type 10...exists.
None of these things line up with the reasoning that "combat ships have 8 or 6 utility slots" as a given rule.