I'm having trouble understand if it's

(0.60) x (championlevel) = AP total

or...

[(0.60) x (championlevel)] x (current AP) = AP total

The formula is (.6 x champion level) + current AP = AP total

I'm pretty sure it's .60xchampionlevel = AP added to your total AP. Hence at level 18, you will get a bonus 10.8 AP that gets added to your AP, not multiplied to (that would be pretty insane).

~Sadness Assassin

In any case, Archmage's Savvy should never be taken, the critical strike chance will obviously do more damage then a skill whose ratio is 1:1. One critical strike does more than that already.

Funny, the first 2 heroes you mentioned autoattack quite a bit. Anyway, the point is, +10 AP at level 18 (or +5 at level 9) is negligible, especially since if you care about AP (and thus have good AP ratios), you'll have so much that +10/5 will seem basically be non-existant. And that's a best case senario!

During the laning phase, where an edge is more important, it provides pretty much zero benefit. At least that extra crit strike helps you earlygame.

I'd rather have the AP later, albeit not much, then the crit early. The laning phase ends around level 6-8 or 10-15 minutes, after that I don't find myself auto attacking very much, but that's just my playstyle.