How come the champions with the most outdated models 
are not tier 1 while others 
who surely dont look that bad are in higher priority? Udyr Jax and Fiddlesticks models should have the highest priority.
I think the reason for that is a lot more goes into the decision behind updating a champion than just "outdated visuals". Sure that's a major driving factor in choosing which one to update next, but there's a bunch of other stuff that goes into it too (game health, potential of archetype, thematic resonance, etc).
I did a AskRiot awhile back that went over how we choose and prioritize VGU candidates. Link Below
http://na.leagueoflegends.com/en/news/community/q/ask-riot-chromas-and-champup
Fiddle is actually Tier 1 now.
And its also partly based on their gameplay health and the fantasy that the character represents.
For example 
is our "floating blades" champ,yet she plays like a regular bruiser and uses her floating blades for only one skill(and they feel incredibly lame in that skill)
And Volibear is likely this high because they said that they actually have a really nice concept to make him into a bit more than just a talking bear
While binary, Udyr and Jax find some success, though Riot tries to keep them out of the meta because of their binary nature (panth fits under this as well)
If a champ can't find any success at all without being busted, that's when they need to be tier 1.
they also need to know a new direction to take that champion in that fixes the issues while still keeping them similar enough.
Do they still have Pizza Feet?
(In all seriousness it's probably just what Valor Bot said.)
I thought Fiddlesticks was tier 1.
