User blog comment:Lukeatlook/Pyro's Item Overhaul 2 - Diversifying Mages/@comment-8468980-20140316072707/@comment-8468980-20140316194352

""Mega Haunting Guise" already exists in the form of Liandry's Torment."

No, that's an upgraded item that grants an onhit effect. I referred to the item that may benefit them better as 'Mega HG' because it would grant more mpen and AP, which would benefit this subset of mages better than Liandry's.

"but keep in mind that every midgame item, even is designed for "oldschool mages" such as Xerath or Cassiopeia, can just easily get abused by "mainstream" mages such as  LeBlanc,  Gragas or  Ziggs ."

Assassins yes, utility mages no. Assassins scale with extremely well with early flat damage stats and penetration so they'd most likely merc this kind of item. But utility mages value lane sustain, harder scaling items, and a little sturdiness to stay in lane as much as possible and to keep their damage from being irrelevant later in teamfights. As for Ziggs and Grag, Ziggs may be a little overtuned and Grag is getting completely reworked to be an AP bruiser.

"Mages already dominate midgame."

Assassins and utility mages yes, true ap carries not so much. Lulu's recent popularity despite Xerath's rework and Velk's release is a testament to this.