Right now the most effective raid exotic seems to be GHORN for basically it's effectiveness in taking down crotas shied. It's not essentially required my team can easily beat CROTA without it. Come HOW I believe the most desired weapon is going to be the thunderlord for those arc shielded enemy's. And also since it has never been been sold by xur.
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It will probably be useful for the next expansion. Wreck all the captains!!!