Jirachi and Celebi has 100 base in each stat, as do Mew, but since Mew is able to learn every single attack (exept from Draco Meteor, Frenzy Plant, Blast Burn, and Hydro Cannon), it is so darn unpredictable that it is über.
The Wobbster is über due to the fact that it might trap and counter almost anything due to its ability, and its insanely high HP stat. Adding encore to it's arsenal, it is DEADLY, and therefore über.
Shuckle, to be honest, I don't know. It has insanely high def and spec. def, and is more of an annoyer rather than a wall, but as stated, I don't know.
Latias and Latios is guaranteed to carry soul dew if you are facing it in the metagame, (since it boosts their special attack and defence by 50%) but if you are talking about the chance of getting it when you catch them, that should be 100% when you go for the other Lati@s.
(If you chose Latias, then Latios will be holding the soul dew at the Nintendo Event Island)
Hope I helped :)