online atm is on the downside, but server is still full i.e you can go to a zone and pvp for spot in 5mins Many of the top cp's including mine are currently playing on the new ru off since we are bored of patch 1.5. Patch 2.0 is currently on the open beta test and should come some time soon, so there will be huge surge of online when it comes. The server is 2 years old and always has had stable online, you shouldnt worry about that.
Activity generally comes in waves depending on the season ( less online during summer ), more during winter, for example during december-march in EU prime hours it was just 5-10vs5v10 pvp all the time for top spots.
I'd say it's the best time to be a lowbie 55-70 right now, cuze most high levels are waiting for patch and aren't 24/7 active which means you can actually farm without joining a side and getting protection.