I do believe Choice Specs Heatran does the same thing Taunt Heatran does, with more power, no recoil, and another move. I suggest Choice Specs Heatran>yours. You don't have to run Explosion any longer, so you can now use Dragon Pulse for dragons, while running your preferred choice of hidden power to hit Swampert/Gyarados harder.
If you want to use Heatran w/out Specs, I would have to say Magma Storm+Explosion is much more successful. Plus, you can trap Cresselia if they want to combat you, or trap Swampert and follow up with HP Grass. IMO it just seems like Taunt+LO is really quite counterproductive since it forces you to take their attacks+LO recoil, meaning Seismic Toss Blissey WILL beat you, since you have no HP EVs, it only takes 3 Seismic Tosses and 3 of your attacks. Or, 4 Seismic Tosses and none of your attacks. You will especially be in deep shit against HP Ground/Fighting Blisseys.
If you want to use Heatran w/out Specs, I would have to say Magma Storm+Explosion is much more successful. Plus, you can trap Cresselia if they want to combat you, or trap Swampert and follow up with HP Grass. IMO it just seems like Taunt+LO is really quite counterproductive since it forces you to take their attacks+LO recoil, meaning Seismic Toss Blissey WILL beat you, since you have no HP EVs, it only takes 3 Seismic Tosses and 3 of your attacks. Or, 4 Seismic Tosses and none of your attacks. You will especially be in deep shit against HP Ground/Fighting Blisseys.