Like many, I have issues with how Ran'jit was handled; it's one of the few missteps in the overall fantastic story.
There wasn't nearly enough information about him in the main story line to explain who he was or how his skillset worked, beyond he's been fighting sin eaters for decades and raised and trained multiple Minfilias. I don't even mind his power level or how his weird martial skill was unfamiliar enough to baffle the Scions for a time until we "figured it out", but the lack of info was more frustrating in this case than making him scarier. Possibly because of the issue with having had Zenos behave in similar fashions where we "have to lose the right way" as he consistently beat us over and over in Stormblood, and so Ran'jit felt like more of that same frustration.
I also feel like maybe Ran'jit started off decent-ish, but was hardened by the hopeless situation of the world, and his "love" for the Minfilias felt more like an abuser's; he trained them to fight and be vessels for the Oracle, not their own person, and Ryne he kept locked away, ostensibly to "protect her" but that in its own way was abuse. While some of the Scions (I think wrongfully) assumed Thancred couldn't tell between the Minfilias, it was Ran'jit who demonstrated in his dialogue the inability to see Ryne as her own person, separate from previous incarnations.
His popping up in the pyramid in Rak'tika also felt very plot-directed, rather than naturally written in; did he have a way to track us specifically, maybe some way to home in on Ryne? Because how could he get through not only an uncharted forest but also the maze and puzzles of the temple to meet us in time? And then again, more plot armor.
I too really think Ran'jit should have been defeated at the trolley duty in Ahm Araeng. He was Thancred's foil, Thancred's villain, and things were set up for it with Ryne's special cartridge she gave him literally just before the battle. The story was between these two men as her father figures from that first meeting in Laxan Loft. The duty in Eulmore felt tacked on, and only to satisfy the requirement of "it's the PC who is the hero and gets the kills" even though 1) the setup of this expac giving the Scions more agency and depth as party members works, and 2) we were controlling Thancred at the time anyway.
The Jesters could have been the dangerous enemy duty blocking the way to Vauthry, instead of doorstop sub-bosses. I felt like I killstole Ran'jit.