None of that matters....

XZ Ultimate.... AOE knockback.

I almost never travel around the map with 0 stacks on mana tankassadin. Dunno.

So let's say I go into a fight with 0 stacks, and get to use the ult 3 times.
That's 6 bases and 3 APs

Under old, that's 720+1.5 AP
Under new, that's 480+2.4 Ratio.

So the 0.9 ratio needs to cover 240 base, or 266 AP, which dunno when you see on tank kassadin on Dominion.

But that's the optimal situation for AP Kassadin.

Ah, I see where I went wrong. I did the calculation on a single event, you did the calculations over a series of jumps. I was thinking, you're zipping around the map and start combat with 4 jumps, how much AP would you need for that 5th initiating jump to make up the loss? That would be 250 AP. If you look it as a series of "I hit the 1st jump, then hit the 2nd jump, etc.", how much would that series lose. In that case, your math would be correct.

Ikruti, your math is still wrong.
The stacks don't benefit from the AP ratio.

If I have the 5th initiating jump on the enemy:
Old: 5*120+0.5 AP
New: 5*80+0.8 AP

So you need that 0.3 AP ratio to account for 200 damage, or in other words, 666 AP.

Konfetarius, I had a more or less full build non-RoA Kassadin game this week. 99 AP from AA's passive, 45 from it normally, 70 from Void Staff, that's rounded up to 210 with the bit from masteries/ignite (I take the AD masteries in T1).

Still not equivalent.
And this is only equal/better for the first scenario, where you join the fight without stacks. The more ults you get in a fight, or the more stacks you have before you join, and the more of a nerf it is.

And if you built pure AP Glassadin, then still, it's a buff, so long you don't get into a fight with many stacks/use the ult numerous times in the fight. And if you built glassadin, you don't really have the mana to do that anyway.

I know the stacks don't benefit from the AP ratio and did my math as such. This issue is that I was looking at the contribution from AP as 0.8, when in fact the contribution would be 0.3, because the 0.5 is accounted for and irrelevant for figuring out the change.

The equivalency formula is really:
(120 * jumps) + 0.5 * AP = (80 * jumps) + 0.8 * AP
(40 * jumps) = 0.3 * AP
133.33 * jumps = AP.

Then I'd use sigma notation for the summation but meh, I think we all get the idea at this point.

Dominion was the impetus for a lot of the upcoming Yorick, Kassadin, and Urgot changes, yes. I didn't make these changes myself though--that's the domain of live team in general. But yes, we'll be keeping Dominion balance in mind now.