[Banshee]'s Silence makes enemy Necramechs unable to cast abilities.
If you're going solo, it's best to use silence against Voidrigs just to [Protect] your Companion from his mines.
Against [Bonewidow], don't use Silence, just destroy his arms and hit his back when he charges at you.
Keep your 4 active during the whole fight with no problem using this build.