I thankfully haven't stepped foot in Terminal C in over 2 years - but I always recall the security lines being unacceptable dating back to the CO days.
It's just a bad system: 3 massive lines going into 3 piers with only 4-5 TSA staff on staff at a time with those useless blue coat public workers bullying pax around.
It's MUCH MUCH better in Terminal B with DL. They have a brand new security area and seem to get people through rather quickly - even when the AMS & CDG flights leave.
Sidenote: Ever notice when you go outside of Terminal C to get a cab there is a public worker attendant that has to arrange the cab for you and negotiates the fare? EWR is so grease-ball - makes me ashamed of the state I grew up in.