Full Legendary paladin, viable at least at ranks 20-15 (just reached ranke 14 with a 7-win streak series).

Val'anyr + lots of heals seem to make it pretty viable in Paladin.

I never succeeded to build a full lengedary with Warrior, Warlock, Shaman and Mage. With those classes, you have too few heals and comeback mechanics.

With Paladin, you have access to a LOT of heals Crystalsmith Kangor, High Priest Thekal to counter Alexstraza, Wickerflame Burnbristle and Ragnaros, Lightlord, plus the weapon from Uther of the Ebon Blade.

Add Val'anyr  and Sunkeeper Tarim as control tools, a few resilient minions and taunts, and you can definitely have good matchups at least in low ranks and have fun showing your collection :-D