Have you seen Generator Servant from M15?  T3 hasted Heartless seems awesome.  Also, Dictate of the Twin Gods seems perfect.

I had to tweak some things to protect myself from life loss via Heartless Hidetsugu. I added Loxodon Warhammer, Basilisk Collar, Platinum Angel to protect against Heartless Hidetsugu + Grafted Exoskeleton, and Platinum Emperion to protect against Heartless Hidetsugu + Gratuitous Violence. 

I'd consider adding some hasters, because no one is going to let your general stick around for a full turn: heat shimmer (under new legendary rules), reckless charge, jawbone skulkin, anger, thousand-year elixir, ashling's prerogative, crimson mage, etc. Hall of the Bandit Lord will do the same.  Oh, and Urabrask the Hidden.  Steal-type cards work too: threaten, word of seizing, act of treason, act of aggression, mark of mutiny, traitorous blood, etc. All will haste your own guy or steal an opponents.

I like your damage doublers, maybe add overblaze and/or quest for pure flame? And grafted exoskeleton, because if your opponent is over 20 life, your general will 1-shot them with poison.  I'm tempted to suggest some lifelink equipment, like basilisk collar or loxodon warhammer, but I think if you hit with your general you're in good shape and don't need the 20 lifegain. But in a multiplayer game, it may make sense.

I'm not sure about the land destruction board wipes, but red wipes that don't do land are kind of hard to come by.  And colorlesss non-land wipes can be pricey: Nevinyrral's Disk, Oblivion Stone, All is Dust, etc.  If you like leyline of punishment, sulfuric vortex? May as well run Valakut, the Molten Pinnacle since you're monored. 

I like that you've got direct damage spells with X, but I'm not crazy about lightning bolt, magma jet, and their variants in EDH.  Unless they've got two modes, like Urza's Rage.  You'd want to wait until after pinging with your general to use them, otherwise they're only half as good, and even then they're maybe ok as creature control.  I'd go for more board wipe-y burn, like earthquake, magmaquake, blasphemous act, pyrohemia, etc (especially with repercussion).  Or failing that, maybe some colorless ramp or mana flare ramp instead? I like hostility too, can triple burn damage and Deathforge Shaman which can be devastating with enough ramp.

This looks like an awesome deck.  I was considering a mono-red Krenko goblins deck, but this looks like so much more fun than a pile of goblins.