Ok. I think you're sorta trolling but I'll chime in with legit answers, not an opinion (per your holy paladin reasoning)
1) Holy paladins can roll need on items THAT DO NOT HAVE +HIT (most players frown upon rolling need on gear with
Spirit also but that's not a rule), caster gear wise. Does not matter if it's Plate, mail, leather, or cloth. The
statement "holy paladins can't roll on anything BUT plate is untrue.
2)Rolling for ANYTHING WITHOUT Spellpower would be for OFFSPEC. IE you can't roll on plate legs that give Attack
Power, Armor Pen, Strength, or Agility. Those items will NOT have spellpower.
3)Mp5 is very quickly phased out BUT that still doesn't mean you can't roll NEED on said item, since it fills your
primary need of INT/SP as a caster/healer and all gear with MP5 is considered Healer gear.
To sum it up, learn what Off spec means, It doesn't seem like you do considering the overall vibe of your replies. You can't roll on MDPS items or Tank items as a Holy Paladin.