A couple of things to change:
His ult range could be decreased but Caitlyn's ult range needs to be increased
Seems good. I had a similar sort of idea to bring more power to his ult, since in it's current state it's only good for dodging a ward before ganking or cutting off an escape path. The way I see it, Mantheon is, thematically, one of the most aggressive and reckless champions in the game. He shouldn't be using his ult to sneak a ward, he should be using it to brazenly crash into his enemies at the cost of his own safety.
Current ult: Grand Skyfall...Range: 5500 (700 impact radius)...Cost: 125 mana...Cooldown: 150/135/120 Active: Pantheon begins channeling for 2 seconds and, upon completing the channel, leaps into the air and becomes untargetable. He then blinks to the target location and plummets down, striking after 1.5 seconds and becoming targetable once more. Enemies within the impact zone take 200/350/500 +50% AP magic damage, increased by up to 100% based on their proximity to the epicenter, and are slowed by 35% for 1 second. If the channel is cancelled, Grand Skyfall is put on a 10 second cooldown.
Modified ult: Grand Skyfall...Range: 3000 (700 impact radius)...Cost: 125 mana...Cooldown: 150/135/120 Active: Pantheon begins channeling for 1 second, signaling a target location visible to his allies. Upon completing the channel, his target location is revealed to enemies and he leaps into the air, becoming untargetable. He then blinks to the location and plummets down after 0.75 seconds, becoming targetable once more. Enemies within the impact zone take 200/350/500 +50% AP magic damage, increased by up to 100% based on their proximity to the epicenter, and are slowed by 35% for 1 second. Pantheon deals 100/200/300 true damage to himself, reduced by 50% if an enemy champion is damaged and, if his passive is available, it will be consumed to reduce by 50% again (75% damage reduction from both occurring). If the channel is cancelled, Grand Skyfall is put on a 10 second cooldown.
Currently, the counterplay to Pantheon's ult is to walk calmly away from the target location. With these changes, counterplay becomes more about gaining vision of Pantheon with diligent warding, since you can't just walk out of his ult unless you gain vision of his approach and run away preemptively.
P.S. Champion changes usually go in Gameplay. Concepts and Creations is more about art and skin concepts.
I think is E ability needs the most help,i rather have it have true damage than the q
