Sated Devourer doesn't just affect champions

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Keep in mind that you will be glass cannon until you finish those items and then start building tanky.

You probably won't even need Last Whisper. Devourer will give you plenty of Damage when combined with the AS of those items, Regardless of how much armor the enemy has stacked.

True, but with enough armor they could turn that 16% of current health into possibly 13% or less(not gonna say any less than that, because I've not quite grasped the math behind armor and MR quite yet).

And a lot of characters are glass cannons that have their own self-defense(Yi, Irelia, Aatrox, etc.).