I Think only Abyssal Sceptre should get 10% CDR, and not Hourglass, at least not both.
That's just overdoing it a bit, I don't think both of these items should receive 10% CDR but I do think one should.
In my opinion it should be
and not
but Id settle long as it's just one that gets it.
I personally use 10% flat Cdr runes on most of my pages but even If I didn't, there are still various AP+CDR items that I already build frequently/are available(
[Hextech Belt 6.9]) and I usually struggle with trying to avoid going over the CDR cap more than reaching it.
And what about AP Tanky/Hybrid's? I'm not going to list every single CDR item but there are many champions that have various viable builds and playstyles including
and or
.
That is not to say that there is no more room for AP+CDR but I think it's really just 1 item that needs it and that's Scepter, not Hourglass(but like I said, either one is fine).
I guess my point is, there will be more people struggling to not go over the CDR cap than less people trying to reach it if both of these items get 10% CDR. Simply put, it's overkill because Riot has already done a good job adding more CDR to the game and it's dangerously close to being too available.