So, let me get this straight.

Necrons currently rely on Dolmen Gates for FTL.

Dolmen Gates connected to the Webway, but the Webway amputated most of them, so now there's effectively a Dolmenway and a Webway that function exactly the same, but the Webway is much much bigger.

Ergo, Necrons can only be relevant if there's a Dolmen Gate nearby, and the Dolmen Gates are few and far between, yes?