The newest PBE build revealed a new AP item, Plate of the Warmage. This item now builds into Zhonya's Hourglass instead of Chain Vest.
Plate of the Warmage
Builds from Cloth Armor + Cloth Armor + Amplifying Tome (300 + 300 + 435 = 1035)
+25 Ability Power
UNIQUE Passive: Killing a unit grants 0.5 bonus Armor and Ability Power. This bonus stacks up to 30 times.
Cost: 125 (Total: 1160)
It's just too expensive. Building this thing sets you up for a Zhonya's later, but compare this to the current scenario. If I'm facing an AD mid or an enemy AD gets really fed, I need to get some armor. My current options are Cloth Armor(s) or a Chain Vest. Currently, I build Chain Vest, because at a cost of 720g, it gives me +40 armor. This amount is satisfactory at a decent price, and will also build into Zhonya's later on.
Compare that to the new situation. If I want armor now, I will have to build Plate of the Warmage. This causes a whole slew of problems:
1. I have to spend 1160g to get LESS armor, in addition to a decent amount of AP. I could just get the Cloth Armor(s), but that takes up more inventory space for less armor even still (600g = 30 armor). This makes it a good idea to wait until you have enough for the entire thing, and that alone will set you back quite a bit of gold and hurt your item flow. It's simply too expensive to warrant purchasing in the situation of "dang, this AD mid is killing me, I need something to get back on equal footing." The only way you'd have this much cash is if you were killing people or farming REALLY well, and you wouldn't be rushing to build it if you were dominating him. If you are losing and you DO take the time and farm to save up for this, you're investing quite a lot into this instead of whatever your main item progression is (which should be toward Deathcap, usually, unless you're a mana hungry champion). It's useful if an enemy AD gets fed and you need an answer should he come your way, but even then you're forced to spend more money than the current option.
2. The passive on it suggests you building it early, leaning it toward being a better early/mid game item. In order to make the most of this item, you need to build it sooner rather than later. If I need armor immediately, this item will provide some armor, but not to the extent of Chain Vest. Eventually it will be a positive benefit, but even still, you're spending more money (440g more) for +5 armor and +40 AP. Yeah, the AP is really nice, but that's NOT why I would go out of my way to build this item: I need armor. When I need armor, I want a quick, efficient answer that will build into something later on. Chain Vest was a decent priced option that cut my damage output growth for a bit, but now we're being forced to get this instead (or the cloth armors, which hurts your inventory space). This means I have to spend more money to get the defense I need. The only real benefit I see is being able to grab a cloth armor after dying/going back as a soft cushion to their damage output without worrying about it being wasted (now it will actually build into something).
The big problem here is that it builds into Zhonya's Hourglass, replacing Chain Vest. Chain Vest fit the niche it needed to do, giving you a decent bulk of armor immediately, when you needed it. It was a modest price and did what it needed to do. Now, we're being forced to get this instead, which in my opinion, is a negative change. I liked the idea of another item to build in the case that I needed something early on for armor as a mage and didn't have the huge cash for a Zhonya's, but I just want the armor. The AP is nice, but I'm being forced to spend more money to get the armor I need. I COULD just get a Chain Vest regardless of this item, but now, it builds into nothing useful later (unless I simply just go for GA). This is in addition to the fact that I (in addition to many others so far) feel that the passive simply disappearing on upgrade is negative, strange, and feels like a loss.
Riot's design for the item also helps to encourage a Cloth Armor + 5 potion setup against AD mids. Personally, I think encouraging Cloth Armor + Health Potions similarly encourages poor gameplay. This helps turn the lane into a passive lane, similar to starting with a null magic mantle+pots or flask+pots. This turns it into a farm lane, and discourages offensive trades/fights.
This also goes against their philosophy for changing the top of the defensive mastery tree, which was the fact that easily obtained armor/MR discourages offensive lanes, and prevents skilled enemies from killing their opponent (when they should be beat out).
While it also provides a starting item choice option, it also would discourage the use of AD mids if there was too strong/too common of a counter to them, even if it just makes it less fun (a difficult to kill enemy that can't really fight you back due to no offensive items).
I think that starting with a Cloth Armor shouldn't be the "go-to" against them, but purchasing a Cloth Armor and being able to make good use of it upon returning to the lane is a good option. You shouldn't simply assume that you will need defense against them at the start of the game, which would be the same as assuming you would always need a null magic mantle at the start when seeing an enemy AP mid. Yet, even still, the item contradicts itself: if you build it cause you're taking too much physical damage, you have to pay MORE money for LESS armor than Chain Vest. The only way it becomes decent is if you stack it up fully, and that doesn't make sense (you rush an item that needs growth to effectively counter something you need armor against immediately?).
Anyways, I think the intent here was good, but I would prefer some tweaks before it went live. As cool of an idea as it sounded when you guys announced you would be adding a new early/mid game mage armor option, this is negative in addition to the benefits it provides... making it questionable. If this is intended to be a buff to mage survivability options, it becomes questionable due to the nature of which its being implemented (cost, Zhonya's change, etc).
My possible alternative would be something like...
Plate of the Warmage
Builds from Chain Vest + Amplifying Tome (700+435 = 1135)
+30 Ability Power
UNIQUE Passive: Killing a unit grants 0.66 Ability Power. This bonus stacks up to 30 times.
Cost: 315 (Total: 1450)
+Allows you to get the armor you need immediately, while also providing you an additional interesting optional upgrade upon going back to base for AP
+Passive encourages upgrading, provides interesting gameplay and decisions
+Still gets more armor upon building into Zhonya's, encouraging the upgrade
+Upgrade becomes more efficient than a Blasting Wand alternative (compare: cost of upgrade 750, vs wand cost 860) if you manage to get a good amount of stacks, encouraging skilled farming
-Slight cost increase wouldn't be a bad thing, possible alternative is 1500
-Passive could be something more interesting, seems to simply allow you to lower the cost of the item while giving it more "maximum" stats. I still feel (in addition to others) that upgrading into Zhonya's and simply losing the passive feels negative, strange, and like a loss.
-Could POTENTIALLY compete with Needlessly Large Rod in terms of efficiency, but purposely kept maximum AP down to minimize that, could reduce further or increase cost
-Removes ability to grab quick cloth armors upon going back early on in the game. A potential fix would be Cloth Armor + Cloth Armor building into Chain Vest.
Thank you for taking the time to read.
EDIT: This was intended to go in the PBE forum. My apologies if it doesn't fit here.