EDIT -- Now would you look at that, 0/0 Naive Heatran takes 55.1% - 65% from a +1 LO Modest HP Rock (50.2% - 59.1% if it's Timid, forgot to add) and does... well, a shitload of damage with its own HP Rock to Urugamoth. But it doesn't kill it and it's slower, so it's actually 2HKOed!
Gotta say, been a fan of this guy since day one. I love fire types and the element of a fire moth concept just seems cool. However, and hopefully this is just me reading this sentence wrong, you say that "it doesn't kill it and it's slower, so it's actually 2HKOed!"
I read that as Heatran gets 2HKOed by Uruga and that Heatran can't actually kill Uruga. The fact still stands that Heatran (Substitute Set with Leftovers) does 93.9% - 111.9% to Urugamosu with HP Rock at 70, now I might be wrong in thinking that he can hit 70 with his EVs, but even then after 2 rounds of LO Recoil from Uruga, he only has to hit 80% of the health which is not that hard.
Just for some reference I used Moltres as the typing for the 4x weak to rock, changed the HP and SpD stat to 85 and 105 respectively, then used a timid nature with no EV's in HP or SpD.
So in terms of Heatran, he's a hard counter to this guy, being able to come in on the BD, and sub up or just beat on Uruga. However, with that being said, Heatran will become AMAZINGLY more predictable now that we see pokes before a battle. But at that, ScarfTran still wrecks this moth. If you hit HP Rock on the switch you get Tran to around half health due to no boost but get killed by HP Rock from him since he outspeeds, if you BD on switch then you only get 1 HP Rock in before getting killed. Same goes for sub set.
On that note, I have to question your Damage calcs again because I have HP Rock doing 44.9% - 52.9% to Sub Tran from Timid +1 LO Uruga, which means even then you only 2HKO with SR and barely without SR. ScarfTran takes a bit more a bit more at 50.2% - 59.1% (Which is what you had), which is a clean OHKO but considering that Sub set won't even be 2HKO'd without SR which, in a new game with no spin blocking, isn't hard to prevent. So I still see Heatran destroying this guy unless properly scouted.
All in all I like this guy, I feel he has quite enough moves to substantiate a position in OU, although I'll bring that up later. But Heatran was the same way with everyone noticing his glaring 4x Ground weakness, and even then he still became top. This guy will definately be a game changer due to the few hard counters he possesses, and his stat spread + boosting move. At the moment I see both Bulky and Offensive Gyara OHKO'd with Rocks, which I feel this poke will have to have a team that can keep it up, Uruga also OHKO's Salamence without rocks, these are both with HP Rock. So in the end Blissey and Heatran are all I see that are stopping this guy during sweeps, I could be wrong or missing some pokes, but I really see this guy having an effect on the game.