There has always been raid-exclusive exotic weapons, but not armor. Raid armor now just provides benefits when killing an enemy type and doesn't provide any benefits to the raid, like D1 did. Raid-exclusive exotic armor could sort of be this way of implementing those kind of benefits for raids. They can provide a major benefit while in a raid, but also provide a minor benefit for general use, so that they aren't exclusively useful in the raid.
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Maybe not armor, but what about exotic ornaments or something for the raid armor?