I asked this same question and honestly, ROI will have higher items dropping so there is no point in raising in such a hurry if your 300+. Just doing the story will probably boost you up quite a bit.
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probably won't be getting rise of iron, but best of luck to you. If anything I'll just get ROI so I have all DLC for Destiny... I think this is Destiny's last dlc until they move on to Destiny2, right?!