devourer shyvana is op as all hell right now. Hell, devourer on anyone with on hit effects in there kit if op right now (diana, kayle, etc).
After it's eventual nerfs, there are damage dealing junglers out there. Rengar is one of the better one's right now. Trailblazer for farming and sustain into warrior and latet add the first part of hydra for more sustain. From there, yommus, last whipser, and some tankyness for full build (unless you wanna go full ad and delete people.
Shyvana is great without devourer as well. Build Bortk and any jungle item of choice (besides magus) and go full tank. You'll do a lot of damage in fights while being almost unkillable.
Masteries don't make much of a difference. if you want a tanky jungle take the defense masteries and include the ones that have to do with nuetral monsters, vicer versa for damage jungle. Rune pages are the important part. You need flat armor seals since all jungle creeps do physical damage. For glyphs you can go what ever fits your jungler (cooldown reduction, mana regen, etc.) and if all else fails just take scaling MR. Marks will of course be whatever helps your damage best. I go armor pen on rengar and hybrid pen on shyvana. For quints, I go movement speed since I use the same rune page for most of my jg and movement speed helps all junglers. You can go attack speed on junglers like xin zhao on shyvana but again, it's up to you.
And you could always go ap sona or ap lux if you want a support that does damage.