Runeglaive wasn't needed, all Magus needed were buffs
My Magus +80 ability power +20% cooldown reduction +250 Mana Passive: Restores 20% of damage dealt against monsters as mana.
Build Path
+ 
+ 
That was all, the CDR and ability power is alot more useful than the on hit AOE for AP Casters like Fiddle sticks where as Diana benefits nicely from the Runeglaive not many people benefit as much as you might have hoped Riot. Fiddle doesn't get to auto between heals and I think that you should really have left Magus as a standalone enchantment and just added Runeglaive.
This list is my opinion on which champs would benefit more from either Runglaive or Magus
Magus Users:
(AP)
(AP)
(AP)
Runeglaive Users:
Something to note is that the Magus still would work very well with those who benefit more from the Runeglaive but not necessarily vice versa
