Funny that you list 3 of the jungle items that can have each enchant... well, that's a separate thread anyway.
I don't see anything wrong with the current state of Warrior, but I agree Devourer needs some improvement.
If jungle enchants are intended to be primarily distinguished by class and what stats the champion wants, I don't agree with also tying Devourer to a different power curve than the others, especially one that makes it so weak when you first build it. Just because a champion likes to autoattack and AS is a strong stat on them doesn't mean they shouldn't be allowed a power spike when they build their jungle item.
Farm scaling dependence has never really worked that great; it encourages hard farming, which Riot doesn't really like anyway because it's less interactive, so then they nerf it into the ground (on top of the massive weakness it already has in lack of presence to help the rest of the team with lane dominance and early-mid objectives).
Yes, I know Warwick was an abuse case (although that was partly the onhit form of Challenging Smite, which has been fixed anyway), but either he or Devourer or both were overnerfed. Autoattacker junglers shouldn't be completely useless for 30+ minutes. Especially since they're also often squishy melees, which gives them a weak late game even if their items are scaling hard at that point (because they can't survive going in on a team).
IMO it would be better for jungle items to have an on-build power spike comparable to most non-jungle items (not things like tear, junglers can't afford that) and maybe some slight farm scaling in addition. Since junglers are typically behind in exp and farm, it wouldn't hurt for their items to be slightly better than normal items, as long as it's not so much better everyone else starts taking smite to gain access to them (like the OP versions of Cinderhulk).
Maybe the effect could be divided into a per hit and a DoT part, like Teemo poison? That could make AS valuable, but not too valuable, and "hit X times in under a second" abilities good, but not totally broken.