You have to remember that Champion is a US based server (west one I believe) so while it is 5h30 pm for you it's barely morning for us which will explain the low population.
You might have more change with the European servers which have a population based closer to you. You will need a different updater to access those server though but you can find it on the NCsoft website.
There are more Australians on champion then some would lead you to believe. Come on in and welcome aboard the drama boat.
However if you're after a large population during our peak period timezone I would advise either freedom or justice.
Luv Elly
There are a few around Champion, and I've seen many on Justice when I do laps on that server.
We have several Australian's on our server, most of 'em are pretty good folks. I'm sure Bud will post in this thread already but he's a top notch guy. We run all scrapper TFs off and on. 
I'll always be a "Champion" at heart. My server away from home.
"When the people fear their government, there is tyranny; when the government fears the people, there is liberty." - Thomas Jefferson
"With great moustache comes great responsibility" - Zee Captain
Just as an FYI to help you get a true picture, you can tell which server has the most activity at a given time. When you log on, the most recently accessed server is at the top. The rest of them will be arranged in their order of activity, with the most lightly used server in the second slot and the most heavily used server at the bottom.
I would also encourage you to go to the Oceanic Lounge:
http://boards.cityofheroes.com/forumdisplay.php?f=667
You may be able to connect with more players in your area.
Thirdly, see if there are global channels that you can get on. There is nothing that can make a server seem more populated than to see the server chatter scrolling up the side. I've been surprised at how many people were on at odd hours of the day even though the zone seemed pretty dead.
Elly is right, its Justice and Freedom you want. Beware though, there are some fruitcakes on both servers, of course.
If you do go to Justice join the Australia channel. (/chan_join Australia) Its a public channel so anyone can join.
They run TFs/SFs nightly and they prefer to run Villian side, mostly. 
I play on Champ because its the best bunch of people I know, the feelin' is that of a tight family, black sheeps and all. Plus the drama its some sweet sweet stuff, makes me giggle. 
And Horus, we needa do another all Scrap TF. I creamed my pants on the last 1. It was that much fun.
Hello, im new to CoH after playing from the very start of CoV.
Was wondering what is the most active server you would reccomend for an Australian? This can also include not just Australian population but Americans that play at 12-10am ish time (Basicly our night time or ever bit before then like after school for me)
: And on a side note, can anyone tell me how big the 'Going Rogue' expansion will be to download? Because where i am our exchange is telstra dominated. Low caps, very high speed, high cost and it isnt worth it...
We are switching to 25gb up from 10gb plan so can you atleast tell me it will be under 5 gb? I can chew 10gb easily without downloading anything over 200mb sadly..
Cheers in advance guys!
EDIT: Well i just started the trial and it seems i wont ever play this till it actually picks up if it does..
5:30 PM Friday night, 33 people total across the entire villian side and 60 on hero.
Sorry but im going to stay clear of this game if its like this, too bad WoW is the only mmo with active and populated aus servers :/