Okay, I re-designed again, for this my mega-cheese legends deck:

2 x Flamecannon
2 x Frostbolt
2 x Annoy-a-Tron
1 x Bloodmage Thalnos
2 x Explosive Sheep
2 x Mad Scientist
2 x Duplicate
2 x Ice Block
1 x Echo of Medivh
2 x Fireball
2 x Polymorph
1 x Baron Rivendare
1 x Loatheb
2 x Sludge Belcher
1 x Emperor Thaurissan
1 x Sylvanas Windrunner
1 x Flamestrike
1 x Dr. Boom
1 x Kel'Thuzad
1 x Alexstrasza

Okay, this is a super-fun deck, although I'm not sure if opponents would agree. I've played about 10 games, and am on a big win streak with it so far.

The fun with this comes from "discovered" combos through all the different combinations of the legends plus whatever triggers duplicate. It's very very versatile but has no overall "plan". And may lack a proper win condition.

Echo of Medivh is killer in this deck too. If there are two or three of the bigger legends out and they haven't cleared them, an Echo is devastating for them.

I've had the duplicate copy most of them now. If it's Loatheb, then that sucks for them. If it's Slyvanus cool. If it's Bloodmage Thalnos, cool. If it's Annoy-a-tron or Sludge, cool. If it's Dr Boom, which it has been a couple of times, amazing.

Some combos:

Baron Rivendare + Sylvanus - if you drop the Baron as Sylvanus is attacking to die, you get TWO of their minions. Really not bad.

Baron Rivendare + Dr Boom - if those bombs live for whatever reason, the Baron triggers them twice. Also deadly if you can use Echo to copy the bombs. Also, it will be hard for them to take ouf the Baron if Boom is still on the table.

Annoy-a-tron + Duplicate + Kel'Thuzad - if this ever happens and they have no removal it's probably game over.

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The only one I'm not sure about in here is Emperor Thaurissan. On the one hand, he can produce some cool broken turns like Sylvanus + Sludge Belcher. Or Bloodmage + Frost + Frost + Fireball + Fireball -- which happened once. But I don't know if he's that useful, and he's probably the one I want duplicated least (aside from the Explosive Sheep, which I usually trigger with the hero power as an anti-rush measure vs. Warlocks etc.)

So far though, this has been a solid deck. Can run into amazing combos, and if the Annoy-a-trons or Belches don't come out for whatever reason, I can also use the old Ice Block, Ice Block, Alex routine to get back up to 15. If they can do 15 damage in one turn after that, they deserve to win anyway.

Oh one thing more: for some reason this deck has absolutely annhilated any Warriors I've come up against. Wipes the floor with them!

More:

Kel'Thuzad + Bloodmage Thalnos

Kel'Thuzad + Sludge Belcher (+ Baron Rivendare for maximum screwage)

I'm starting to think the deck doesn't really need a win condition, it just needs any of these sick combos to trigger for a win.

that looks like a lot of fun