The design problem with "bonus on-hit" and Devourer

I don't think I'm saying anything earth-shattering here, but I'll try to do so succinctly and clearly.

The problem with items that allow the user to get additional procs of on-hit abilities--the most notable being Sated Devourer--is that they tend to be terrible on the majority of champions, but awesome on a few who have on-hit synergies baked into their kits (e.g. Warwick, Kayle, Shyvana). In order to prevent the item from being totally broken on these champs, there are a few options:

1. Nerf the item's statistics. This basically turns it into a niche item that is only useful on champions with specific synergies. I phrased this in a somewhat negative way, but I think this is a legitimate option. This is basically the solution used with Runaan's Hurricane, which is just 92% gold-efficient and consequently built almost exclusively on Kalista.

2. Nerf the champions who synergize with it. The issue here is that you'll likely have to nerf multiple champions, and you make them reliant on that item, posing more problems down the road if you rework or remove the item, as well as restricting alternative builds.

3. Make the bonus on-hit a small part of the overall strength of the item. This makes the synergies a nice bonus rather than a major purpose of the item. An example of how to do this with Sated Devourer would be to add something along the lines of "Damage dealt by Phantom Hits is scaled by 0.5," "Cooldown reduction due to Phantom Hits is scaled by 0.5," etc. The problem here is that the solutions can be a little inelegant (such as the example I just gave).

I'm not recommending a specific solution with Sated Devourer, but merely pointing out the design pressures that force items like this either to be niche items, or overpowered on certain champions. Currently Runaan's is on one end of the spectrum, and Sated Devourer arguably on the other (though the process of stacking it balances that out somewhat).

One last thought: Currently, Sated Devourer has a gold value of 2700g (Devourer is worth 2100g on purchase), while Warrior is worth 1877g. I understand there are multiple reasons why this is the case, but still, that's a pretty big disparity for two items that cost the same (never mind that Sated Devourer has a passive and Warrior doesn't).