Mages have shitty defense items and poor items specialization for a wide class of class of champs.
The only decent AP defense is 
and compared to 
, its kinda crap. All the other defense items are health AP items which makes mages look like tanks with 2500-3000 health.
To top it off, all mages use the same items. AP assassin, battle mages, artillery mages, control mages, APC mages, AP fighters all use the same 
On the other hand, ADCs have a full and diverse item set, AD assassins have their own items, and fighters have their own items. And they can still use items from other classes if they want like garen can build 
.
AP itemization lacks depth and specialization both defense and offense and its sad because they keep doing a shitty touch up update instead of giving mages real options.
Mages need specialized items for DPS, burst, artillery, melee offense/defense range and control. Right now, mage items is just a generic blur that serves all classes of mages.
(with real tanky stats)
provides a shield ok but you need to trigger it and it costs mana
needs to stack
Others mostly give HP
And the ones that provide HP
