The damage it provides is negligible, not worth noting. It's -literally- not worth my time to get them for the amount of damage it does.
Have you actually looked at the amount of damage that it does? It's not an insignificant amount, nor is the fact that it can actually take a fair number of hits before it dies. Hell, getting to use Heroic Moment simply because you're Bioan was *disgustingly* good, especially since it's an ability designed for *solo play*.
Secondly, you still get to gather mats as a Bioan, in every single FP. All of them have dogs you can rip mats off of. Arch doesn't get to do any of that. Even if you got nothing else, you'd still get the benefits of gathering mats while doing the FP so it's *still* not useless.
"Useless" specifically means "of no use". In order for Bioan to be useless, the pet would need to deal no damage at all (which it doesn't) and provide no mats whatsoever for the FP (which it doesn't). Bioan *still* has a lot of use to it. The fact that it doesn't provide the bugged ability to use the solo play mega-CD of doom when summoning said pet doesn't make it anywhere *near* useless.