Bane already applies the 60% reduced potency to all targets beyond the first, and the duration reset only affected them as well, so I doubt it'll be used in the manner you describe here. It's still more DPS to just time the reapplications of the original set of DoTs with new applications of Tri-Disaster or hardcast Bio/Miasma. It would need the iron jaws effect to be worth attempting at all, and I suspect they'd make that reapplication work in the same way as the rest to save on dev time, meaning it'd have the same 60% reduction and full duration reset, and therefore not be worthwhile compared to hardcasting on 2 targets provided enough time was available for full ticks.