Note; after Absolute Virtue they will never do something like this again, but they should make a boss that is unbeatable by design.

They just don't tell us that. Tell us the boss is in fact defeatable.

And proceed to release said boss that changes strategies and battle tactics at the drop of a hat, randomly dropping all aggro on the tank and start cleaving the dps for no reason before suddenly jumping wildly, switching weapons and abilities and generally being impossible to strategies around.

Once that boss has been released, SE should catalog and study the results.