I've been playing almost everyday for around or over 4-6 hours farming the new destination's gear while distortions are active so that it guarantees T5 weapons on heroic public event completions. To this day I have yet to obtain a T5 Seventh Seraph's Revolver. There must be something wrong with the loot drop tables or percentages since it (and a handful of other weapons AND more interestingly, certain perk combinations) seems almost impossible to drop.