As an elf sampire, I rarely need med. With latent MR4 from conjurer robe and sash I get back just enough fast enough in non-med to cast confidence quickly. Then go honor a sheep and whammo, instant regen.
There's never a lack of innocent stuff around to slay to slake your thirst for mana. (gotta keep it sampire toned

).
As mentioned throughout thread, too many variables involved for a blanket answer to apply.
I voted no, based on the assumption that it is elf sampire template. I dont see the point in MR on a PURE PVM sampire. That slot is best used on something that supports an active role in combat. The dribble of mana otherwise is just not going to give you that edge as often as others. Not that it WONT, just not as often. For example, HP regen 2 on all pieces or SR 3 will keep you alive far longer than MR. Imagine SR 28 on your character (+10 from vamp, + 18 from all woodland suit). Would not need stam leech OR cast divine fury much, which might free up an additional weapon slot, so you could have HLD/HLA on weapon and not miss the mace and shields.