I didn't like the current run sitting at 12 minutes, it was only ever a placeholder run and far from optimal so here is a proper effort. Sliding in under 8 minutes feels pretty solid, I know there is room for improvement but I'll settle for a solid time for now.

So there is quite a bit going on here and its not helped that I made a few mistakes.

The basic idea here is to trigger the Necron arrival and then get the reinforcement waves as quickly as possible to deal with the Monoliths. The reinforcements can be triggered intentionally by deleting units at the right times after the Necrons arrive. The general order of events is: