Devs, Stick to your guns or remove Viera all together.

[HollowedDoll]

Of the 32 canon primal fights in game, so not counting songs and simulations, nor things that are not primals:

19 of them outright mention fellow adventurers. Link.

12 are relatively ambiguous, mostly variations of 'you must face off against such and such.'

1 explicitly says you fought alone. Tsukuyomi.

Roughly 60% of Primals are confirmed as being fought with a party. That is pretty much the opposite of the vast majority being solo kills.

So we gonna ignore the lorebook, then? Okay. Half of these don't even make sense since Ravana and Ifrit aren't situations you knowingly get yourself into. Susano is literally a parody of the phenomenon.