Easy answer to the current tank meta state

bring back the old , have it so they can coexist maybe allow them to be traded like you had for Finding a decent means of armor pen should be a cinch.

I think what you did for worked out great and this would work in a similar fashion.

or one like it: 300 hp 10% cdr 10 armor pen 60 dmg same passive. without the phage

and 400 hp 20%cdr 40 dmg

http://i.imgur.com/fGpDUGm.jpg

Atm, if you want mana and you want black cleaver you're pretty much already siting on 30% cdr. which true its always nice to have cdr but sometimes you don't need it that much and are fine sitting on 20% especially if your only sitting on like 250 mana or no mana items at all for that matter.

black cleaver isn't being built much also because mana options are lacking as well in non cdr form. triforce is your best bet and it phage stack (not that big a deal but is this the best we can do?)
, both give 40%. sometimes you don't need more cdr to get the job done you just need more damage.

Intuitive selection system. http://i.imgur.com/hssjVYH.jpg

for mana i posted this: http://boards.na.leagueoflegends.com/en/c/gameplay-balance/jTKPyThj-reminder-that-there-are-no-flat-mana-mr-items-easy-fix-available this would also coincide well with the AP item changes.

Alao should just make mana runes free or at least tier 2. since its an important part of the game to have freedom to tweak. Lets make runes a better tool. And meditation could give greater value between regen % of missing mana, or a set flat mana amount if you aren't stacking mana.