Aggro Grenadin

Into the furnace sounds cool, until you realize Torch is a card. I'd definitely replace Furnace with a playset of torch.
You really want the 2 cost 2/1 grenadin that makes another 1/1 when he dies. It fits into your theme of saccing units
If you're using obrak, you may want to conisder dark return. It has a powerful synergy with destiny that shouldn't be overlooked.
I've never been impressed by powderkeg. I'd cut him as soon as you're able to afford more of your legendaries, or you have a gearcruncher. I think crunch would be a solid topend for this deck.
Also, you definitely want more crests.
More copies of scraptank would also be great.

I'm not thrilled with the warhelm in your market. You may want to cut it for some removal. Imo Obliterate is great because it gives you some reach and kills alot of things in the meta