Yeah, start of turn. And I suppose it's a demon too.
It's kinda interesting in how it's a prime target for your opponent to try and remove as soon as possible, even though its effect is not immediate at all (that's not to say it's bad, it's very powerful in any control match). But your opponent will still spend a good removal card on it, conserving one of your larger, more immediate threats.
EDIT: welp, if it's start of game, then nvm most of that. It's not a threat to your opponent, it's not that relevant from Bane either. It gives your deck 6 potentially bad draws (cuz a Pit Fighter isn't the greatest). Good for heavy control and fatigue, where every card is value, but it doesn't fit other decks. It's alright in Arena though, but since it's legendary... yeah, how often are you really gonna draft this.
I'm just another one of those. You know, those who do things. Things that need to be done by those that do these things in order to do those things that don't do these things themselves. Has the word 'things' lost meaning to you already?
Am I the only one that isn't that impressed? I doubt you want to play this guy on curve against an aggressive deck since you're increasing the chance of drawing a high-cost or below average minion, and while he gives you a huge fatigue advantage, it's unlikely another Control deck wouldn't be able to kill him. That, and the fact that Doomcaller is probably more insane than this guy.
The class in which he has the most potential is Rogue, because of the Stealth effects, but we all know that class has never been particularly good when building greedy control/fatigue decks.