[Messianic]

Even at the lower levels (10-20ish), grouping is fairly easy. As has been mentioned, the freeport area has the most activity, but there are definitely hubs elsewhere. Gfay/Crushbone is very active, although there are mainly levels 1-8 there, along with a few wizards who might be porting in for various reasons or people passing through to Unrest...

But with 900 people on, don't expect to find anyone in somewhere like Erud's Crossing (although there are occasionally people there and in the other isolated areas).