The very first line of your OP says: "Every week we get " maintenance " that is always extended."
There is no assumption here, you said "Every week", that means every week.
I don't believe it's a bug, and it's not so much the Keywarden 1-shotting, as it's you 1-shotting yourself. When Dune Dervish mobs begin their spinning attack, they will reflect all projectiles back at their caster. If you're blitzing the Keywarden with Bolas, or Rapidfire, or any other high-damage attack (especially if you're well geared and very powerful), you will deal incredible damage to yourself, very quickly. I've lost DH this way as well.
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There is no assumption here, you said "Every week", that means every week.
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