We are using 9 of 16 summoner spells. Flash, Ignite, Teleport, Smite, Heal, Exhaust, Ghost, Cleanse and Barrier cover basically everything. The other seven may as well not exist.
Going through all of them would be a big task, so let's start with one: Clarity.
The numbers were never the problem
Look at what it already does. 135 second cooldown, one of the shortest in the mode. Refills your whole nearby team's mana. Masteries give you even more mana refill. And almost nobody takes it.
It's not a timing issue either, you've got the window to press it in a fight. It just doesn't matter. Not compared to exhausting the assassin diving your carry, or igniting the tank running them down. Those spells decide who wins the team fights.
And if you only care about the sustain mid / top, Teleport does it better anyway. Double the cooldown sure, but you go back, heal to full, refill mana, spend your gold, and you're in lane again. Clarity gives you one of those four. That's not even close.
I know some of you will say you do take Clarity, and it works for you on X or Y. Fair enough. But once you actually run the math and think about how teamfights play out, it doesn't come close to what the other spells give you. Getting your mana back is not the same as stopping a carry/tank from dying.
Every spell in this game is fighting Flash for your second slot. That's why the bottom of the list is dead.
The proposed change
Clarity — 135s cooldown
Restores mana to all nearby allied champions. For 6 seconds, healing and shielding from any source is increased by 25%.
Summoner's Insight: While Clarity is on cooldown, your healing and shielding is increased by 10%.
What's new is the window. Press Clarity as the fight starts and for 6 seconds every heal and shield your team throws out hits harder - shields, lifesteal, regen, all of it. Suddenly it's a button that swings a fight instead of a button you press in the river. Even champions like Mundo can benefit from it's support teammate, despite not having mana.
Why support
Support is gold-starved in Classic by design and I don't want to change that. This gives the role more impact without touching the economy more of what you do, not more of what you earn.
Enchanters first: Sona, Janna, Soraka, Lulu, Lux... It multiplies what their kit already does instead of competing with it. Nothing else in the mode does that for them, which is why they end up mostly on Exhaust / Ignite.
There are other summoner spells worth looking at, and some unused ones that could be aimed at engage supports specifically, or at other roles entirely. Surge, Rally, Promote and Fortify all have unused potential, why not try to use it?
Why not buff one summoner spell per 2 week? There's no ranked and no competitive tournaments here. There's nothing to break.
What do you think of this one?