I would say the 10 best Legendaries of the set are:
Patches the Pirate ( Auto-include in very pirate deck)
Kazakus (Should be very strong. At the very least it's going to be a ton of fun)
Aya Blackpaw ( can easily be as strong as Highmane and makes your other golem cards better)
Wrathion ( I would be surprised if this isn't an Auto-include in dragon decks)
Raza the Chained (Very strong effect, makes Beardo playable and buff Paletress by a lot)
Inkmaster Solia ( A very spell for the class with the best spells? Should be very strong, could make Rafaam playable)
White Eyes (Extremely strong in control, probably strong enough for midrange,too)
Wickerflame Burnbristle ( Can easily save your life against aggro, might be good enough for goons)
Kun the Forgotten King (Either a 0 mana 7/7 or a mega shieldmaiden, both if you somehow have fandral on the board)
Don Han'Cho (Not really sold on this one yet, since I don't have a good picture of what goon decks are going to look like, but could be very powerful)
Also,I think Mayor Noggenfogger is slight better than he looks at first glance.
His effect really fucks with any kind of combo deck.
Having said that, he stats are most likely too weak.