The only reason I have ever used /WHM when levelling, besides getting stoneskin early, was the ability to have some of the -na spells w/o having to be in addendum, maybe I switched to dark to do something and didnt have the JA to use addendum (sleep an add, and then say tank gets silenced or para'd)
I have never used /blm, lack of buffs is fail imo.
And on a side note, I have a couple blm/sch's in my LS that do endgame events w/ it, they control their hate very well and are able to outnuke most /rdm's thanks to cheaper spells and can sublimination when they get up, until they rest, which is a great help since don't often have a RDM to refresh their party
As for food, hMP will always beat out +MP in the long term, you can start out w/ +30 MP over someone w/ +5 hMP, but after 6 ticks of resting, they have got +30 MP more then you and will be able to get up faster for next mob (noticeable when soloing puddings, I rest very little compared to most blm's i see, thanks to parsimony and sublimination and high hMP)
For healing, mushroom stew is definitely full of win