I didn't like this quest line. It feels strangely leveled for when you get it, and the ending is not only unsatisfying, but feels like it railroads Aloy into a decision she would never make.
Firstly, this quest line begins with fighting a pair of Ravagers, followed by a Thunderjaw, and you likely find it as the first side quest upon entering the West. It concludes (with an extra side quest in Scalding Spear, to be fair) with fighting a Thunderjaw and a Stormbird together (kind of). The difficulty is fair, but really shouldn't be available before seeing Hekarro. Maybe this is a quirk of Ultra Hard, but the starting level of 17 is not high enough. At least the ending is marked as level 30.
In terms of story, Aloy doesn't get enough time with Drakka or especially Yarra to ever side with either, in my opinion. She has no information outside of hearsay from either one. Is Drakka ambitious? Sure, but I don't see him make enough mistakes from that to see that that's all he cares about. Is Yarra lying to her people, I guess, but for very good reason. It's not that neither is a good option, that can be interesting, its that I, as the player, am never given enough information to make a choice that feels worth killing over.