By the time you get Essence Reaver, you really don't care about mana anymore.

Ashe of all champions definitely wouldn't need the mana leech by the time you can afford the item.

Remember, this is not an early game item. It takes a heft amount of gold, meaning by the time you get it, you'd have levelled up quite a bit too.

This is actually an intelligent point, and I can see a potential for Kog, never thought of that.

On the other hand, what will you be missing out on if you buy this for Kog? Considering his long range, he also has great synergy with Bloodthirster too as he'd be able to activate that sweet sweet shield.

But here the difference between Tear and Essence Reaver.

The Tear is cheap, meaning you'll get it when you need it. Essence Reaver is expensive, meaning by the time you get it, you'll also have levelled up quite a bit too, to the point where mana is a non-issue unless you're Swain or Anivia.

And with Essence Reaver, you're just gimping yourself because you could easily just forego it and buy a stronger AD item instead. It's Passive mana regeneration is a waste of gold because the narrow list of champions who can make use of it won't even need it by the time they get the gold for it. How hard is it to understand that?

Look, anyone who knows what they're doing will know just how useless the item is on in champions that'd want it.

No amount of mana regen could help Maokai.

I really like this approach because OP is right, as the first few levels are usually pretty rough because you're always wishing that you have 400g to spare when you go back for a but by the time you can get 2650g, you're usually ok. My thought was to toss in a charm or two or maybe even a since it already gives 10% CDR as a middle ground, but an intermediate item with a slightly toned down passive would probably be a more elegant solution as it does feel weird to buy a component item that gives you constant regen only to make that regen conditional when you upgrade it (although gives precedent to this).

She can do that WITHOUT Essence Reaver. Okay, no champion can spend their mana on a spell permanently. But for Ashe and her Q, she can use it more than enough time before returning to town either via death, injury, or to buy crap.

And last time i checked ardent censer was op with nidalee(85% attack speed when your heal is used and maxed). (Before she was changed the item may not be as strong with her).

I barely see any Nasus at all, but the few I see only had mana problems pretty early-ish in the game.

By the time you buy this item, especially now when they changed it to a late game item, Nasus should REALLY not worry about mana. They have Triforce for that extra bit of mana anyways.