In that case, I think the pungi in question should also have a stirge-like blood drain, especially since the authors of the ToH were the founders of our own Creature Catalog!
Hmmm, ok, I guess you've sold me on something more potent than Con damage. But "one life level" sounds more like energy drain than Con drain. What if we do that?
Anyway, if we agree it should be a separate critter rather than an underbar, should we finish the standard pungi ray first?
I kind of think that, since we're making a whole separate magical monster, I'd like to go whole hog and make it energy drain. But we can decide later. "Vampire Pungi Ray" will work.
Back to the normal one...
That would be fine with me. I don't feel a real need to change the basic ability scores any.
On to the spines?
From the original text, it seems they don't really attack actively --- they always flee when attacked themselves. I'd stick with the spines as a more passive hazard-like thing.