The current issue people are having with Ardent Censer is that the % heal/shield bonus it and Mikael's is not unique, and it is additive rather than multiplicative. Supposedly this is because you want people to buy both Ardent Censer and Mikael's Crucible without a loss in efficiency. However, what really happens is that they just stack 5 Censers and a Deathcap or something like that. I have not done the math but apparently it's too much.
* Problem - Ardent Censer stacking is OP!
* Solution - Make Ardent Censer's +60 AP Unique!
Why does making Censer's AP unique help? Because then you only get +15% Heal/Shield Power, +10% CDR, and +50% Mana Regen for 2400g, not only making it lose a lot of individual efficiency, but the less AP you have the worse off your base heal/shield is so the % isn't working with nearly as much.
Is it a good idea? Who the fuck knows? I didn't do the math on this, either! Get the hell out of the Gameplay board, DTN!