I used tarns quite a bit, years ago. Mostly Havoc's. Tarn combat was sorta fun, back then. Was sorta cool, as Tantus described. Meaningful. Tarns were powerful but tricky to use. You could have good tarn battles in the sky. You could have an impact on the ground, though it was by no means true that you could take on several defenders on the ground yourself, without support on the ground. You were air-support.
And yes... there was this odd 'Rau' battle going on between Dove and Havoc (and some others). And of course, as happened all the time in SL Gor, you had the conflict of interest: Realism/balance on the one hand (for the good of all players) and individual fighters wanting to be bad-ass/the best fighters possible on the other, with the last motive being stronger than the first.
Something else played into it too: Those sims that focused on fighting, mostly (usually 'GE' sims) were already inclined to ban tarns altogether. They wanted to have a level playing field. And they wanted it for all genders (femlaws, panther-girls, etc.). Tarns came with this whole lore-based thing about who could realistically use them (which is really mostly city warriors, of which the pure combat sims had far less, and maybe some outlaws, like Tarl himself in outlaw), questions about where they could be used (could they be used in the Tahari, Shendi, Torvalsland, the Northern woods, the islands, etc.?) and there were already tiny 'fly anywhere' tarns around. So, many sims already banned their use. 'BtB' sims usually didn't really keep up with the technical side of things as well as the combat-focused sims.
Of course, Gor, filled with feuding sim-owners and group leaders with massive ego's, competing visions of what Gor was supposed to be, competing creators and individual players always looking to be the most powerful they could possibly be, never did manage to seriously collaborate on creating 'standards' for combat that would ensure some balance and realism for the combat side of things. It always an ever-changing chaos, with some sort of balance occasionally emerging and holding for a short time, until some new OP thing came along that wasn't banned by most sims quickly and managed to get used by a majority (which then made it impossible to get rid of because sim owners or their buddies and/or Masters would be among the ones using it, and no one in SL Gor ever wants to give up using anything). It seems Tarn combat was just fell victim to this total lack of self-limitation and organization.
SL-gor is a nice micro-cosmos of what it would be like to be ruled by the Freedom Caucus.