Same Combat Power, twice the damage

Combat Power counts what you own. It can't see what you did with it.

The game measures the difference itself. Skill Index scores your damage on a boss against everyone within 20 Combat Power of you, where 100 is the median. kanonxo, who has cleared the Korean pinnacle raids, has posted 238 against that median in the 560k to 580k bracket. More than double the damage of the median player holding the same number.

None of that gap is gear.

One skill is more than half your damage

Gladiator and Templar take over 60% of their total damage from a single skill. The rest of the roster is less extreme and the shape is the same: a short-cooldown skill you press constantly, and a lot of big numbers you press rarely.

The repeater is the one whose level matters. Ruinous Blow hits for 2,387 on a 45 second cooldown; Overhead Slam hits for 174 every five seconds and takes the cooldown off entirely once you level it. The second one is your damage.

Five of the eight have their cooldown removed or reset outright. Cleric gets the reset one tier earlier, at 12, and multi-hit at 16 instead.

Spiritmaster works differently. There's no cooldown to remove, and Elemental Fusion's level 12 perk turns it into a charge skill worth up to 200% more damage. Your summons matter too: each Summon skill gives its spirit +20% stats at 16, so levelling the summon is how you raise a spirit's damage.

Every class also has a Rampage or Scattershot skill whose level 16 perk takes a second off all your cooldowns when it lands. Sword Aura Rampage, Flash Rampage, Storm Rampage, Arrow Scattershot, Flame Scattershot, Lightning Strike Scattershot, Gust Rampage, Rapid Scattershot. That's your second skill to level, after the repeater.

Level 16 hands you the perk, level 20 lets you equip it

Specialty perks unlock on a schedule, and options and slots arrive separately:

The cooldown removal on your repeater is that fifth option, so at 16 you own it and can equip two of five. At 20 you can run it alongside the crit or multi-hit proc from 12. That's why 20 is the number people repeat, and it's a step change rather than a slope.

Levels past 10 come from ring stat lines, Arcana cards and the Daevanion boards. Rings are the slot to care about: their second pool is active skill levels, which is the whole reason a ring with a mediocre attack roll can still be the better ring.

A perk is a multiplier, a gear score isn't

The community damage formula ends like this:

... × critical damage × Double Chance × front/back damage boost × skill specialty enhancement

Specialty enhancement sits at the end as its own multiplier, in the same company as critical damage and Double ChanceKorea calls this Smite. Flat attack from a gear upgrade goes in at the front, where it's one addend among many and competes with everything else you're already carrying. The formula has the full shape.

So a +15 weapon with your repeater at 12 loses to a +10 weapon with it at 20. That isn't a close call.

Four lines worth a reroll

Per point, measured on the stat weights model:

Those four are worth rerolling a slot for. Combat speed is the one people underrate, because more attacks per second multiplies everything else on the list, and it's also the one your ping eats into.

Attack bonus is the trap. It reads like a damage stat and it's worth +0.34% per 10 points, the weakest line on your sheet once you're geared. It goes in before attack increase multiplies, so a crowded bucket has already swallowed it. Take it on necklaces and earrings only because those slots offer little else.

Pet Genus is the only stat you choose outright

Everything above is a reroll you hope lands. Genus slots are a choice, and slot 4 of the Special Board is the one that matters: it's the only place on the boards that carries Double Chance, the best rate on your sheet. Auto Analyze lets you name the stat you want rather than hope for it. The Pet Genus guide has every board's slot 4 and the order to spend in.

Do the repeater first

1. Your repeater to 20. Ring lines and Arcana first; the third slot is the payoff.
2. Your Rampage or Scattershot to 16, for the second off every cooldown.
3. The Genus Special Board's slot 4 to Double Chance.
4. Reroll for combat speed and attack increase on the slots that offer them.
5. Key passives after that. Korean players push some to 25 and beyond, and a lot of damage sits in them.

Then look at your gear score.

Skill coefficients, cooldowns and perk tiers are the client's own, via aion2.app. The Skill Index figures and the 60% share are kanonxo's, from the global revision of his progression guide.