An idea for Essence Reaver

Similarly to how Elixir of Wrath restores a % of damage dealt from all physical damage rather than just auto attacks (like lifesteal), perhaps Essence Reaver should do the same, allowing its 10% lifesteal and mana-vamp to be proc'ed from abilities, which in my opinion defines it from Bloodthirster its AD Caster counterpart item.

If this seems like a viable solution, there are a bunch of mechanics that already exist in some items which could be used to balance the item without having to constantly tweak base values to seemingly arbitrary numbers (remember pre-rework Ryze and Kassadin?). You could steal the stacking style mechanic from Guinsoo's Rageblade and have it gain stacks every time you cast a spell, increasing its physical damage spell-vamp/lifesteal thingy. You could give it an active; you could give it a stacking passive; you could probably even give it something along the lines of a lesser item with the same effect injected into its build path, similarly to how Athene's has Chalice in its build path, but a weaker version of its unique passive.

There are plenty of avenues which could be taken to balance this item properly whilst giving it a defining characteristic such as letting abilities benefit from the lifesteal, just like Elixir of Wrath.