I am constantly seeing people in Infected space, destroying the 4 generators then people wasting time attacking the normal spheres.
Once the 4 generators are down there are 2 objectives only. Destroy the transformer as fast as possible, and make sure the nanites don't get close. The normal spheres are just there to distract you. Ignore them. By attacking them all that is happening is time is being wasted on the clock and you run the risk of a nanite getting through.
I see people attacking the spheres around the transformer and even worse is the person on nanite duty actually attacking a sphere before the nanite and often letting the nanite sneak through or get dangerously close.