I guess running out of mana was unfun....

You can thank the AD buffs every class update and the fat tank item nerfs in the tank update for that one

Hell many tanks have it bad too

just because cho gath is broken and zac is overtuned and gragas is as fat as ever doesn't make the tank class strong

it's just a few outliers that are overtuned or too reliable

I disagree with both of you. Most games, Mages disproportionately have the most damage, unless a Caitlyn or Sivir went crazy. A good team can keep a good adc in check. Mages on the other hand hold all the 1 second kill combos (Syndra, Lux, Brand, Orianna, Veigar, Malhazar). Adcs have to get a few uninterrupted hits off on you to really kill, and if you're vs an adc who can do that, you should have chose champions who have peel to get out of range against them (for example, Ornn is a super nice choice to peel champs like Vayne who stick to you like glue, or to peel a sudden Twitch before he E's you)

Now, Mana: 1) From what I've seen in ranked, mages, unless they are supports, struggle with and are cursed by mana shortages. It's almost impossible for any front carry mages to sustain mana in an early game, and most of the meta builds don't sustain it late game. For example, almost every mid mage rushes a Morellonomicon for the early game per level gain of mana recovery. However, some games starting a morellonomicon is a really bad idea. If you are vs a Yasuo, a Morello is not a good choice. If you're vs a Veigar, it might not be a good choice. If you're vs a Brand or a Syndra, it might not be a good choice, because rushing resist is probably going to give you a better early game (you're talking to someone who can almost 1v5 with a tank Ahri, because her base damage is decent, and some games like those with a Yasuo really need her to be tanky to survive long enough to wait out spam and wind walls). Mana builds have substantial risk involved wherever they are played. If you rush a Tear on a support, you are putting behind your build into a Censer or an Athene's (which neither actually offer enough Mana regen to just spam, but a Tear build with them does!). If you rush mana in a mid, you become prone to ganks in many situations.

And let's be real: Mages haven't been relegated to support because of some imbalance of power or mana problems. They support for the simple reason they are low cooldown, high output champs who can push a traditional bot duo out of lane with DAMAGE. Vel Koz went bot because his cooldowns even early game are rediculously low, and his output is high. Brand went bot because he has one of the most abusive kits to use a Spelltheif, and because his skills lend better to hitting 2 champions than 1 (bounces). Lux went bot because her Snare and barrier much better suit the pace of a bot lane fight. If anything, there's nothing in Riot's design really keeping a specific champ in a specific role (I top Karma and Rakan, because they shut down almost every top laner, and I Jungle Leona, because Leona has unstoppable clear and makes wonderfully 90% perfect ganks).

There is not a single mage support played anymore.

Karma, Lulu, Janna support. You might not consider champions like her "mage supports" but I'm talking about supports who build AP items and use spells for damage/CC. Janna might not have big damage, but she's still technically a mage, just a different subclass from one that's taken mid.

Cass is getting a gutting on her early game damage and won't spike until 250 AP, which is 3 items. Orianna and Taliyah are basically secondary supports.

Anivia and Viktor are actually quite weak. Vlad is countered by an 800g item and about half the meta picks right now.

Malz is a joke at high level play, because he just pushes the wave for years.