How about giving essence reaver 5% CDR instead of 10%.
Change its build path too, to give ADCs a way to get the mana sustain earlier (when you need it most) Like how it used to be built from pick axe. (This wouldnt be very cost effective however since it does give mana after all which you cant really put a price on)
And the mana you get won't really be thaaat significant early since it scales off DMG.
Then give it 5% CDR and 10 % lifesteal with a stacking system that burrows from sanguine blade in aram. For up to 15% lifesteal.
Unique: Your basic attacks grant +1% life steal for 8 seconds (maximum 5 stacks).
This would make it a more attractive alternative to bloodthirster. Which gives a shield and more lifesteal but requires that you have better mana management.
It would also have the same price point as bloodthirster.
The way I see it essence reaver should be the goto mana item for ADCs that do not opt for trinity force and need mana source. It can of course still pair well with manamune as it currently does on blue ezreal.
Build path could be lifesteal pick axe into one item that has the mana refund passive. And then add another pickaxe to complete essence reaver. Adding the sanguine bonus lifesteal and the extra 5% CDR.