If you nerfed it hard, like maybe I don't know make it so that bonus strike thing only does half of the damage of the basic attack. Maybe also make it so any healing you get from the bonus strike is also halved. Heck just halve everything on it and it might be balanced because right now all I'm seeing is an overloaded item that is pretty cheap in price and can work in almost any lane, wait what does that remind me of.............. OH YEAH 
(on release).
make it so that bonus strike thing only does half of the damage of the basic attack. Maybe also make it so any healing you get from the bonus strike is also halved.
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The phantom strike only procs on-hit effects, not the basic attack damage, if that's what you mean. Ignoring the Blade of the Ruined King since it is an edge case anyway, you can only frontload damage with this DPS item if you invest extremely heavily into it with almost entirely on-hit effects (which tends to be the case for all forms of DPS, so nerfing Devourer for doing this is literally the most unfair thing you can do). It also means healing from these procs are damn near nonexistent.
Probably shouldn't judge an item if you aren't apparently aware of what it actually does.
The problem with jungle items like this is the same as the wriggles lantern problem. Farm junglers are at a huge disadvantage to other junglers because they have little to no gank pressure, so their team tends to fall behind a lot. This is why farm junglers are usually quite bad. To make farm junglers viable the farming jungle item has to give them ridiculous stats to compensate for the shitty state they leave their team in. This gives us situations in some games where if the enemy jungler doesn't provide enough gank pressure early on and snowball his team hard before your farm jungler can stack his item fully, then one team has a madly powerful champion with a fully stacked devourer with no downside. Devourer and wriggles were balanced around the assumption that by the time it's stacked your team will be at a big disadvantage, so it has to be a crazy strong item to compensate, But in games where the enemy team doesn't get fed from early ganks the item becomes op.
