Just as a note - the plate bonus really isn't worth losing. at level 80 pre-mop, it was worth 200 intellect, and at 85 with mop gear, it's likely worth easily 2-3x that. Given that the non-plate pieces don't have that much better stats (besides the belt, which I wouldn't use anyway) I doubt you'd be gaining anything.
But yes, the shield is definitely worth having for melee cleaves, it'll buy you probably 15% extra survivability against physical damage, if not more.
However if you PvE, go for all the stats you want. I just don't think it's quite as clear cut as you might think.