Zilliax is the Swiss Army Knife of Hearthstone. Useful in almost any occasion. Rogue as a class has very limited healing and no taunt minions so Zilli is a great option and acts as a removal tool too. One of the few cards that's almost never a bad idea to craft. He wil still be in Standard for the next 4 and some months so I think it's def worth the 1,600 dust.
Even if you don’t play wild, you can still use him in the occasional tavern brawl and solo adventure post-April, so I’d say do it. 4 months is a long time to not have one of the best cards in the game if you are playing a lot.