ok so I get the Eth TM Fort hate because prices were bonkers, but that said...
When I was finishing my 99 push, I was doing solo P8 TZ and had BIS gear outside of charms. You're not one shotting everything in P8 96 TZ (mob type, affix type, etc. matter), but yes things die quickly. The TM Fort said was doing noticeably more damage than the Insight setup and helped my finish my leveling faster. It also pairs better with a high roll Ars'Dul Mephistos (benefits from the damage more on TM than on a Insight base). Since I was burning out on leveling, it was worth it to me to pick up the more expensive items and finish it asap.
Is it worth the cost compared to what you get versus Insight? Not at all. But if you're cost-agnostic it's better.
i have 66k-88k dmg with insight and it one shots everything in p8 96 tz