@riot, The problem with AP JGs has nothing to do with items or mana
I've been a diamond jungle main for 2 years now and I have 2 million points on an AP jungler (elise), so it bothers me to see what direction riot has taken the class of "mage junglers" when after maining one, I know exactly why my AP jungler is or isn't meta and I know about all the other matchups and what sets them apart.
Firstly, I'm really uncertain what riot considers a "mage jungler" because the only true mage in the jungle is 
, everything else is either an assassin, tank, support, or skirmisher.
No matter how much mana or CDR you put on runic echoes, you'll never even out the viability of 
/ 
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and . The reason these champs are constantly pushing other APs/each other out of the jungle is simply put , design efficiency:
is (used to be) a generalist that was extremely flexible in builds, so she could either be an AP carry assassin, a diver, a tank, or a support. When we nerfed her based damage and increased her W ratio, she got pretty limited to an AP assassin playstyle inorder to make the most with her... but the thing that historically made elise so good is that flexibility, fast clear, MS in spider form, and the fact half her kit isn't gated by mana so she's usually more efficient in the "clear then gank" aspect.
is the same way with half her kit not being gated and she has an AoE ability in pounce for camps like raptors.
has a really strong AoE kit (her Q and you can line up camps for an empowered E) making her clears really good, and she even gets a mana refund on an ability if you wait it out. Her ganks aren't amazing early, but you can still work with them and if not, just power farm.
has none of this. He has no AoE for fast clearing, instead he has his single target crow that bounces around.. the problem is this crow is gated by the fact that it can do a lot in a teamfight with auto targetting ,or on half his camps, that you can't even put power in it against the single camps like red, blue, gromp, and the very important scuttle. Season 7 coming is what really put the nail in his coffin, because no only was smite buffs gone, with krugs making his clear better, and raptors buff gone, for vision control, but two more camps became single targets (red and blue) so his crows got nothing to bounce to for repeated damage. Don't even get me started on how long it takes for his W to kill raptors, krugs, and scuttle and how weak his pre-6 ganks are.
This is why fiddle, a mage jungler, can't be fixed with items because he simply doesn't have the qualifactions to jungle efficiently. This is why lane fiddlesticks is a bit more popular since s7, because he makes full use of his kit there (sustain on minions, fear, roaming ults, and crows actually put in work with the wave), but since he's a jungler we never really put power in those roles and focused on power in the jungle, which is beating a dead horse. He needs a rework, either giving him better odds at clearing or a kit re-do in general but with the current jungle in mind.
has been seen in the jungle, but simply put.. he has no use for mana. The passive of echoes, the passive of talisman, blue buff mana regen, scuttle, none of this interest rumble so it feels like he's inefficient of making use of resources given to him. This is why we mostly seen him in the no mana echoes meta because not only did echoes give him the stats he needs, but he scaled really fucking hard with an AoE clear, unlike the other APs which at the time (old eve, elise) fell off or didn't teamfight as amazingly. Add on the fact he's been balanced top lane around LCS and there's hardly any question as to why he is another AP champ kicked out of the jungle.
we proved we don't want in the jungle with her recent changes followed by overnight hotfix, so here's one mage jungler that had potential we got rid of, and if it wasn't for jg morg reasons, it was for mid lane sustain reasons.
And who's next... well that's all the mages but these guys are AP and talked about a lot:
she could easily be a jungler, the problem is she takes too long to turn online and will always be outclassed by evelynn. She needs 6 to reliably gank, her job is to blow up a target or dive on a backline target, and she is gated by needing to land a weird hitbox Q. In the current meta, evelynn can gank pre-6 better then her with a charm proced either with an easy to land Q or her point and click whiplash. Evelynn can delete a target just as well if not better, eve can leave and heal with her passive so she can continue doing her job while diana relies on shields. Evelynn can powerfarm better, and has a way stronger level 6 due to stealth. The problem with diana is she's outclassed and less reliable, but i truely think with just some work she can be a jungler.. the major problem is she's gated by the fact her primary role is mid laner and whether or not her mains would pref balancing around two or one playstyles. She's also in that realm of "diver or assassin" in regards to playstyles so you can either cause something either toxic or she can still be unreliable, but with hexdrinkers, QSS, nullifying orb, etc AP divers in general just aren't as efficient as divers that can build those + GA and steraks.
this annoying little shit hasn't been seen in the jungle for awhile. He doesn't really have the best resources to compete with other junglers that do have way more efficient tools for clearing and ganking, and when you buff his jungle you buff his laning, which historically is a mistake. We also reworked his ult to be more skill expressive less reliable so he's not really the best pick in general for the jungle role.
I see him brought up on the subject of "bringing back AP junglers" but honestly, I don't think its happening. He might have the best chance of coming back to the jungle with his W stun and his gap closer, but he's still inefficient with his clears being too slow, if you want to make him jungle, all I can suggest is bonus damage to monsters on his E or even a mana refund for using E on monsters, because I don't know where you'd want to increase power that wouldn't break lane ekko.
I haven't even seen this guy mentioned in awhile.. he's the same as fiddle, with the jungle changes he's just not good. Less efficiency with talisman against the buffs, outcompeted, low damage until his gets R, overall he's just not as efficient as he once was. True damage on passive doesn't really benefit the current meta where its either unnecessary or does benefit anybody on the comp.
TL;DR: AP junglers just have design flaws in general, no update to itemization will change that so the runic changes don't fix a thing, they're worse then before yea, but regardless either way nothing in the meta will change from them as far as shaking up what AP junglers become good. If you want more AP junglers, you're going have to put that effort into the champions themselves rather then their resources, otherwise by adjusting resources, you globally hurt/buff the ones you don't want to effect.
You're also going to have to re-evaluate the strength of having an AP on the team in general. AD champs just often carry better without being gated by counter items like hexdrinker, or runes like nullifying orb and benefit from those very things too, and aren't gated by what boots they have to go for their maximum output (AP needs sorcs, AD can take whatever which gives them better map presence or better 1v1s against priority targets like ADCs).
