Thanks guys for your replies.
My vote would be for Most Potent at the very least, arguably legendary (very unique effects, especially since you can get more hit points back than you put in).
But if you only get back as many hit points as you put in, the weapons would be pretty weak.
For instance, "
Sublime Genius" would be akin to from a +25 weapon that takes 5 HPs per round when its wielder doesn't take his opponent down or, at best, a +40 weapon that takes 15 HPs per round (when, blahblahblah…)! Granted, the +40 bonus is great, but you can find +30 Most Potent weapons with several other abilities, that would thus be IMO more beneficial to use.
The same way, "
Innate Genius" would be comparable to a +25 weapon, at x2 or x3 damage… that takes 25 or 50 HPs any round when its wielder doesn't take his opponent down. "
Piercer", a Most Potent weapon in the RoCo. VII, is only +10, but inflicts damage x3 to foes wearing non-metallic armor, foes wearing metallic armor being treated as if they were AT1. Whilst being slightly less damaging (as a note, x3 vs. AT13-20 is comparable to AT1), it is OTOH with no drawbacks… and 50 HPs a round is a lot!
I would go with potent, especially for the spear as the wielder immediately loses 11.5% HP upon putting it down.
* - Is the 11.5% remaining HP or of normal full HP? The latter could lead to instant unconsciousness upon putting the weapon down.
Remaining HPs: it's the counterpart to gaining 13% when wielded (1/1.13 = 0.885) so that if someone takes "
Sublime Genius" then immediately put it down, he ends with as many HPs as he had before.
Because you have the negative effects to each, that balances out the Most Potent and "Those Having a Legendary Background" attached to them. Those weapons are all insane bonuses and no negatives. Not only have you balanced out some of the positive with some drawbacks, but you've also balanced it with "...if the foe is taken down, to gain back..." Even the risk of sacrificing HP isn't a guarantee to take down the foe, so that's a gamble too.
If you were to remove any of the drawbacks, then the weapons would go to Most Potent easily.
Ideally, I'd like to have weapons that are Potent tending toward Most Potent.
Have you assigned a weapon level to them?
I have no idea how this works, or what's its use! :p
Anyway, I think one way to consider it is to ask yourselves (or your players) whether you'd take these weapons, compared to similar Potent or Most Potent weapons. As a GM-only person, I cannot alas answer that… and, obviously, I cannot ask my own players since they'll encounter the person actually holding these weapons!