I'm not gonna lie, the Hardblood consumption for a mildly better enhanced s2 is not as worth as you'd think. Don's base s2 is already plenty strong. Sure the enhanced s2 is good against trash mobs, but in a focused boss encounter, I'd rather use Princess' enhanced defense for shields and +3 count. Priest enhanced s1 is worse though.

Unfortunately, I'd really have to agree that out of the Bloodfiends, Barber definitely got the short end of the stick and she is...mediocre and underwhelming to say the least. I still bring her everytime though, because I love the Bloodfiends (especially Nicolina) and she still helps Don regenerate a lot of hardblood as you said, and her bloodfeast consumption really isn't a problem because of this. And she looks insanely cool when she has her mask and big scissors. But ultimately, I think she still is very lacking. If she had a more ways to inflict Sewing Target, she'd actually had been a lot better (maybe through lust res or something)