Ardent Censer should apply to single target spells along with auto attacks.
It'll help increase the comps where it works well, and it'll stop me from being so stingy with my heals.
It can't really be abused any more than auto attacks, Cassiopeia, Ryze and Karthus (and Ezreal but he uses on hit) have spammable abilities that are single target, but will that honestly be more than Kog'Maw or Vayne's 2.5 AS (i.e. you need an ability that's point and click, with 0.4 cooldown, or in Kog's case, 0.2 cooldown. And no mana. And can be applied to another 2 targets if you buy a specific item.)
And supports will have a reason to not just dump everything on the ADC (and occasionally autoing bruiser) and give a huge F.U to the other 3 allies, now they can heal mages and ability tanks too.
and
, instead of 40. Would also like the passive to be better and your suggestion is pretty cool.