A decrease of 22% luminosity seems quite a lot considering that exo-planets usually reduce the apparent output by less than 1% if i'm not mistaken.
Even if it's artificial, it may not designate intelligence, it could be some kind of massive-scale equivalent of a coral reef or ant-hill, a complex structure built over time by simple creatures or processes repeating the same tasks for millennia.
I believe SETI have applied to to focus their observations to that part of the sky following this too, will be interesting to see their results.
What would be more scary - a Dyson sphere half-built or one half-destroyed ?