Yeah, the GP admin has been a bit slack in the last few months cycling the maps around to coincide with patch updates(meaning new maps) so people don't play on them that much. They do get played on, most days, but you're looking at 6pm-12am type buzz. IMO it's the best server to play on
Most people are on clearnetdeluxe these days from the looks of things.
203.97.27.202:27016 (dustbowl, gravelpit, goldrush, fastlane)
203.97.27.202:27024 (2fort instaspawn 24/7)
there are other clearnetdeluxe servers that are populated, but those two are generally the busiest.