Kiln Fiend may have a home here. Love the aggro-burn methodology, +1! Check out mine: Kill it with FIRE!!

the only problem with Kiln Fiend is in this deck Monastery Swiftspear is strictly better being a 1 drop with haste. Otherwise he'd be a great card for me if for no other reason than to bait removal spells.

I've thought about the Swiftspear for my own deck, but it just doesn't hit hard enough, you know? After 2 instants the Swiftspear swings for 3, the fiend for 7. After 3, the ratio is 4:10. I get it, though.

That's understandable because your deck is a slower mid-late game based deck. This one aims to win turn 3-5 so a swiftspear with haste is much more important than getting 1 more power per burn spell.

otherwise I'd tend to agree with you that the fiend hitting harder is much more valuable.

monastery is strictly better because his toughness raises too, kiln fiend need them to have no blockers, swiftspear takes them out. I would suggest getting to at least 18 lands though...