I don't think AP champions need the equivalent of the AD items, but consider this; items are bought for a few different reasons such as
- Helping your champion overcome an inherent weakness (like a slow juggernaut buying dead man's plate, ADC buying lifesteal or GA, or a mage buying CDR to combat long cooldowns)
- Accentuating a champion's strength (this would be like Marksman buying an Infinity Edge, Mage buying Rabadon's, etc.)
- Building to oppose your opponent's strength (Building armor against an AD lane, or MR versus a Magic User)
The problem some mage mains have is that many AD items actually do all three of these things. Black Cleaver for example has a movespeed boost, has AD so it increases damage dealt, armor shred increases that AD damage further, and health and CDR so your opponent can't kill you as easily.
Maw of Malmortius is another, it gives AD for increased damage, armor pen to further increase that damage, MR to mitigate magic spells, and a shield that scales with MR which prevents you from dying to magic damage.
Both of these items cover all 3 buying points, there are more examples but I think by now you understand what I'm getting at.
Now consider the mage options:
Rod of Ages gives AP, health and mana (eventually) which is great, but does not offer any CDR to help mitigate long CD's.
Zhonya's gives AP, armor, CDR, and a nice active, but no health to back it up, and no mana or mana regen so that CDR doesn't quite help until you get a second item.
Morellonomicon gives CDR and Mana, with a mana regen passive if you kill a champion. But without health, MR, or armor, the mage can still be easily killed by an all-in.
I guess my point is that it's easy to feel invalidated as a mage, if Zed first buys
, he becomes very hard for a mage to kill as all his weaknesses have been covered. Meanwhile the mage has to choose between surviving Zed's all-in
, being able to farm effectively
. Zed can easily choose then, based on his opponent's build. If
, he can just push the wave and roam, knowing the mage can't effectively push back without risking running out of mana. If the mage builds
or similar, Zed can just continue to poke until he has an all-in opportunity. No matter what the mage does, it's the wrong choice.
(Man this post ended up way longer than I intended) I'd argue then, not for more shiny toys for mages, but for less toys for our AD counterparts.