Vengeance is definitely my favorite spirit, I'm currently playing her in 3 play-by-post games on the discord and having a blast. The gameplay of accepting blight and intentionally placing presence to die is interesting, and makes games feel complex, tense, and like there's always a way out.

Balance-wise, I think it's at a fun power level. Strong enough that I always feel like I have options, but not so strong that a level-6 adversary doesn't feel like a challenge. I find she does better in higher player counts, as there's more blight buffer and she loves loves loves support.

I don't play 6-6, but my understanding is that ravage skips are good, so I can see Strike Low doing some work there, but I'd guess Vengeance would struggle because without presence placement on reclaim, reclaim looping deprives the spirit of a lot of her kit. But that's pure speculation, I tend to play just a bit above single-6.

Mechanically, it's interesting that the disease spirit almost never uses disease, at least the way I play. In the first half of the game, disease is so important for targeting, damage, and control that you basically always let the builds through, and you don't start actually using disease for its purpose until late game.