on heros like KogMaw, teemo etc.

On teemo i usually get it right after gunblade, as my second real item,
On kog i get it if my jungler gives me the 2-3 redbuff

I'd say after you've got your proc that makes it go. Once you have Kayle's E stacked up, Kog's W stacked up, or maybe even Warwick's Bloodrazor then it's good to go.

I like it on Kayle sometimes. The extra ASPD is Godly on her. I do like to have the extra power of a gunblade or a Deathcap, but If I get the chance I like to get a Malady somewhere around those two items (After my core build of Rageblade + Nashors)

there is no right time to purchase malady.... unless it is a Monday.........THEN ALL YOU BUY IS MALADY

watch your team rage at you when you do

I should start buying it on my AD udyr builds, the dot is magic damage after all!

I buy it on Teemo all the time!

on teemo its the first item you buy right after boots of speed,followed by a madreds bloodrazor.