It would be nice if B2P was useful on its own, so I would vote to keep it preferring to find glyphs first, but past that only focus on walls and no-pass areas (say 1 glyph percast revealed until all are revealed).
I think that there needs to be less syngery between using a health potion and burning it off with B2P (not an issue with Bloodmage, since he gets all his mana back from mana pots). Maybe add a side effect of "absorbs up to your level*2 in healing received, removed on level up".