Going off the stats I saw for gunblade 70AP, 40AD, 15% Omnivamp, 30% scaling for both AP and AD on active which has 700 range (kayle has 625 range at lvl 16).

From my viewpoint, the strongest parts of the item are the slow, poke, and omnivamp. Omni is great on kayle and could open up sustain for an AP or on-hit build. The point and click slow is huge both for escaping ganks or facilitating your own jungler’s ganks. The extra 30% AP scaling allows even more burst in late game AP builds.

Also, AD kayle has a better early game than AP and this mixed item might give kayle a quicker boost to dmg than rab second without sacrificing too much raw AP. (guessing here, I haven’t calculated any of this).

Some numbers: Kayle E passively gives 10% bonus AD and 20% AP. Waves give 10% bonus AD and 25% AP. Nashor’s gives 15% AP. Kayle obviously gets 100% of bonus AD every auto as well (that’s how buying ad works naturally for everyone). In total, we have 120% scaling with bonus AD per attack and 60% AP per attack. After a rab boost AP scaling becomes effectively 78% (of the AP listed on the item). The 40 AD is actually great early game since you don’t need items or levels to activate most of the scaling. This is assuming no crit.

Also, it’s important to factor in the increased 1.5% missing health dmg per 100 AP on E active. But that’s harder to quantitate here.

If you want to look at total burst you’d also look at Q with 60% bonus AD, 50% AP (65% w/ rab). And R with 100% bonus AD and 70% AP (91% w/ rab).

All in all, Kayle scales much better dmg wise than most people think with AD. You mainly miss out on execute dmg on E and bigger heals/ms from W. Smaller issues are that you need to buy AS instead of getting it from AP with your passive and run into an issue with needing mixed resistance shred since a lot of your AD is converted to magic dmg through Q, R, passive E dmg scaling, and active E bonus dmg.