Devourer needs to work on a charge system like the s4 spirit items

the recharge rate can be something like once every 45 sec, holding up to 3 charges so a jg doesn't have to afk farm so hard.

special case of dragon and baron would still give 5 charges free i guess, although i really think 3 would be enough, because 5 stacks from 1 monster is too much of a lead.

either way having a devour jg is like having a nasus on your team, it ok but you'd really prefer a less afk farming type champ.