When it's very dark, it was taking around 5mins at ISO 1600 and autoHDR.So I see, you played more with ISO setting but was it consuming time on site at the night?
You get a quite a bit of flare from spotlights etc..
For sure there is some noise at the higher iso, but nothing like as bad as the image at the top of the thread.
Unfortunately, I'm not permitted to share the images, but if you search the LSF, you'll find some old posts and examples of using istar in low light:
viewtopic.php?f=117&t=7096