The recent dialogue involving itemization has been about 'magnifying strengths and weaknesses', so why then did all of the marksman itemization changes magnify their strengths and gloss over their weaknesses? AD champions (specifically marksmen) have crit, lifesteal, attack speed, and attack damage. Mages get ability power, mana regen (rip), and cdr. But wait, AD champions have Essence Reaver. And Black Cleaver. And Death's Dance. And Trinity Force. And Ghostblade. Meanwhile mages can't take advantage of any 'AD' stats but marksmen can have unlimited mana and maxed cdr from two items that also give attack damage and crit chance. AD champions have the advantage taking dragons, baron, AND turrets. AD champions can deal damage with basic attacks AND abilities. Mages only have their abilities. Mages have waveclear? Build SS and one-shot minion waves. AD champions can build defensively without much penalty (QSS build/Maw + many AD items grant health/lifesteal/anti-burst). Meanwhile Zhonya's active is getting nerfed.
Need a dispel? Build QSS! AP? Better take 
and lose a summoner.
Lanes: AD can go top lane (bruisers/tanks), mid lane (assassins), jungle (dominated by AD. Runic Echoes ends up being abused by champions it wasn't even intended for; Udyr, Hecarim), and bot (marksmen). Mages? Mid...support kinda. Maybe top if you get a cheese match up?
Keystone masteries: Warlords? AD. Fervor? AD. Deathfire Touch, the arguably 'for ap' mastery of this tier, is absolute garbage on all but Cassiopeia or Malzahar and sees most of its use on, you guessed it, AD champions; Jhin and Varus. Not only because it scales way better with AD, but also because it's heavily nerfed for AoE effects which is most mage abilities by default. Stormraiders? Assassins. Then you have the Tenacity tree which is for tanks, but can be used by AD champions (specifically bruisers) to great success. The only option really is Thunderlords.
Why can a marksman have infinite sustain, unlimited mana, max cdr, damage, attack speed, crit, and more** in the same build** while mages get sub-optimal build paths to buy their sole, one dimensional, counter item? And we wonder why we have quadruple AD teams, often triple marksmen, and Rammus flew out into the meta faster than a homeguarded Quinn. Plenty of marksmen bring teamfight/cleave damage (cough Sivir cough) and tanks bring plenty of CC. You pretty much only bring a mage out of necessity for an AP threat. Proof? When the enemy team has no tanks you put an AD champion in every position.
The itemization for AD is just flat out better. AD is more versatile and its items are more loaded with stats and effects. These changes benefit one-kill rotation AP champions and AP tanks; neither of which needed any help. Traditional mages needed more options, more variety in itemization and power spikes, not _more _ restrictions in a meta that already strangles them.
I suppose it's too early to tell what with the updates coming. Who knows, maybe mages will be broken OP. But when they released the AD item changes it made more stats more readily available to AD champions. That's not what these changes appear to be for AP champions, and that makes me sad.
spamming Q building up the blood charge and then negate all their damage with one W...
on lulu (if these changes go thru) would make her a much improved utility bot, while only marginally hurting her dmg output, since her damage never scaled extremely well with ap, anyways.
change will single handedly nerf so many mages that would rush it.