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Typically, as a jungler, you're not going to carry the late game. And as a melee tanky-dps, your role in a teamfight is to keep people busy while your carries burn them down, helping with a bit of damage.
If you want to carry as a jungler, then gank at lvl 2. And then gank again, and again, and again. Shut the enemy team down, and set your lanes up to snowball- give them such an advantage that it doesn't matter how bad they are. If you're lucky, the other team will start blaming eachother and fall apart under the pressure, and you'll have won by the 15 minute mark.
As far as a Shyvana build- I've been going Wriggles, Merc treads, Frozen Mallet, Atma's, Wits End- gives you a fairly well rounded tanky build that also deals significant damage. If the other team tends to clump up during the teamfights around minions, you can even pick up a Tiamats (although it's a bit of a troll item- because it's countered by simply spreading out, although enemy teams that even bother to look at what you're building is rare unless you're fairly good). Because Q in dragon form is an AoE auto-attack, it allows her damage to scale quadraticly (the same reason it's a scary item on Twitch).