Vi is an engaging disruptor that if her team can't follow up on fails to carry games. Also you are talking about two early game dueling champs. They have a lot of ability to invade and disrupt the enemy jungler making them a non-issue as well as a ton of ganking potential. Of course they are strong. But both will lose in a 1v1 vs an equal level/item Shyvana. A good Lee or Xin can still duel them and a good Shaco will frick their world UP.
On top of that if you don't play them right and focus on farming you fail as a jungler, so if that is the person's normal style of jungling then they should not pick them up.
There are three styles of jungler:
Farmer
Objective/ganker
Invader/dueler
Farmers are about the late game. Usually trying to farm to 6 and then either constant ganks or picking off roamers. Objectives like Drag and Herald are usually only gotten with help from team.
Objective/gankers are trying to gank as early as possible, like level 2-3, before the first back and push objectives, tower plates, Drag, Herald, ANYTHING to push the team and lanes ahead
Invader/duelers are counter junglers. They counter gank, steal camps, and disrupt the enemy jungler so that lanes can push heavy and bully. They can gank at 2-3 but generally will gank at 4-6, ie after two or three clears
All of these need to be trying to control neutral objectives and deny them from the enemy jungler, some are better in top side or bot side of the map, and some can be traps to people new to the jungle scene. Farmers especially can be a trap to newbie junglers as they forget to contest objectives and help the team. Invader/dueler can be so focused on kills that they forget to help lanes push and secure objectives. And Objective/gankers can start feeding lanes if they fail their ganks too often.
Some champs can be completely ONE of these things or a mix and its about how you are playing them that game. Some runes and Ults can shift some into new patterns, Shyvana Ult makes her a surprise ganker very quickly, and overall its about how you feel comfortable playing. Right now the early game and the snowball are SUPER powerful in the meta so Objective/gankers are powerful and so can Invader/duelers. Farmers can be VERY powerful but your team needs to understand that you aren't playing to snowball the lanes./
