Also depends on what you consider soloing...
- You can make it to POTIME soloing.
- You can make it past POTIME with one character, but you will need help from others and this is still a huge option on EZ.
There are a TON of players on the server that play 1 toon and progress. Yes, its a slow grind for plat for help or even using some of the one-box guilds. But in the end, they still have 1 player.
I see players all the time with dual 3.0's that just grinding it out helping others and getting help at the same time.
It wouldnt be easy though as the game itself is not meant to really solo.