Huge fan of the TBT-5J as part of a medium raider force. Though it's anemic on its own, I find it makes an excellent battle-buddy for Griffins, particularly the GRF-1N. An extra LRM-15 can add a bit of extra spice to the PPC and LRM-10 rounds the Griffin is already putting down-range, and three medium lasers, though they struggle to threaten heavies and assaults, make a pretty solid deterrent against close-range flanking lights and mediums that are traditionally sent after Griffins and other rear-line fire support 'Mechs. Heck, considering the mobility they have and their intended roles, with halfway-competent positioning the two should have no excuse letting the bulky 4/6 and 3/5 heavies and assaults get close enough to even worry about how medium lasers will stack up to their armor.
Both being 5/8/5, the pair can remain nimble and evasive without splitting up, or split up to quickly add an extra 10 hexes between each other to try and force the enemy to choose between one or the other. I also find that particular movement profile to be the perfect sweet spot for getting my fire support 'Mechs into good firing positions early on, while still leaving plenty of tonnage for firepower.
8 shots for the LRM-15 may not be much, but let's be honest, in a fairly light-and-fast raid, if you don't have a decisive advantage by turn 9 it's just time to call the op a wash and withdraw. Speaking of withdrawing, ideally safely, let's not forget that RT crits to the TBT-5N have a 40% chance of hitting an ammo bin, wheras the TBT-5J's single bin only offers a 25% chance of becoming fireworks (though the LRM can still only soak so many crits). Furthermore, critting a bin with one shot left leaves higher odds of survival, as there's no chance for a chain-reaction crit to set off a shot from another bin (though in either case, setting off two shots is enough to guarantee an instnant coring). Really, the Trebuchet's anemic ammo supply in most SW-era models isn't always such a bad thing; as early versions of the Hatamoto-Chi can attest, sometimes having just barely enough ammo can be a blessing in disguise. Now, once CASE and CASE II become a thing, especially if you can get hands on a Damage Interrupt Circuit or Artificial Pain Shunt? Go hog wild.
So, in summary, would I take the TBT-5J in a defensive mission, or as a component of a slower fire support lance? No way, TBT-5N all the way there. But as someone who personally spends a lot of time playing pirates, I feel people seriously underestimate the TBT-5J as a mobile, reliable, and semi-multirole support platform as part of an attacking force- particularly one concerned with profitable raids more so than strategic victories. It's just got that magic touch that can make a force of other 5/8/5 and 6/9/6 mediums a bit more scary when defenders bring heavier 'Mechs to bear.