Get rid of stealth and its fine. But stealth makes it a bit too much.

“So strong… And only 5 Mana?”  
Ok it summons a Lil’ Woona.  
I’m statisfied. =D =P

@Blissey1
 
Legendary cards aren’t actually meant to be overpowered, they’re meant to just have more interesting/specific effects. Like a Black Knight is a 4/5 for 6, but has the ability to destroy a minion that has taunt.  
Just based on its stats this makes Black Knight a more expensive Chillwind Yeti, but the extra situational effect makes up for the increased cost.
 
Leeroy is a 6/2 for 4 mana, but summons 2x 1/1 whelps for your opponent. This means it’s designed to be 6 damage for 4 mana, which is on par with a fireball. An Arcane Golem, on the other hand, is a 4/2 for 3 mana with a slight downside which in some situations is better, and in some situations is worse. Leeroy just happens to be much more useful in decks that can exploit its unique properties - like Miracle Rogue.

I’d say 6 health is a bit much, and is probably the only thing stopping this card from being decently balanced. Making it a 7/4 would at least put it in range of AoE for it’s cost. As it stands, a Power Overwhelming combo on this thing would destroy games.

@Blissey1  
Translation: It’s supposed to be OP.

@Seergun  
In the same way that Leeroy invalidates every other Charge card, right?
 
come on, it’s a legendary. It’s supposed to put other, normal cards to shame.

I don’t really like this cause it invalidates two cards, Venture co. Mercenary and Ravenholdt Assassin.

Pretty beefy on the cheap and stealth? This will pretty much always trade well.  
Imagine dropping this turn 4 with a coin.

Only 5 mana?