Devourer is pretty annyoying, but it isn't completely broken. There is still plenty of counterplay. You just have to focus on the pre-sated game.
To counter it, there are a few of things you could do (especially in draft where you can see their pick).
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Counter jungle the ♥♥♥♥ out of them. They need their stacks in order to become stated and incredibly strong. If you are continuously counter jungling them and keeping control of objectives, they can't do this.
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Keep wards deep in their jungle (trackers knife is perfect for this) and get your friendly laners to help you.
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If the jungler you are playing isn't going to be the best at counter jungling, focus on fast pacing the game and snowballing your lanes.
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Apply that map pressure, get your laners fed. Progress the game to a stage where the enemy jungler either needs to match your map pressure (taking them away from their precious farming), or loses control of their jungle due to your superior vision.
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If you have failed the above options and they have managed to become sated (or very close to), you must work hard to counter their strengths. Devourer junglers rely heavily on their attack speed. What are you going to do?Buy randuins and frozen heart. Both these items lower attack speed and come with some A+ armour which will also go a long way in fighting them.
Guinsoos is a pretty popular item on dev junglers so it is probably a good idea to involde how to beat that as well.
You must play around the stacks they have. Kite them for a lil while so the stacks can fall off, then go in for a balls-to-the-wall engage (keeping in mind that you have a short timeframe before you have to back off due to them regaining stacks). Frozen heart is also a pretty good counter to guinsoos as well.
Another way of dealing with this item (works best in ranked where you can see champs and guess build paths) is to pick an annoying tank with strong AR and MR, who wont be shredded by the damage _as _ easily (think: malphite, mundo).
If all else fails 
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