Fleetwork vs other precision keystones?

Hey, guys and girls,

So I thought I'd give it a try since I needed the sustain warlords used to provide in lane. Aaand.. I was amazed how little did it provide apart from the moving speed. When I had 4 items( ; ; and with on , this heal almost peaked at 60 health on champions and (36 on minions).

Why would anyone take this over the other two, especially when you have those minor runes in domination as Taste of blood, which provides, funny enough, better healing?