Questions from a returning player.

So after trying out the Tera beta weekend and finding it was not for me, my interest grew in heading back to and checking out Aion, especially now that it's free. I originally played at launch on Zikel, and stayed for about two months before quitting. Now that I am returning, I see that Zikel has been merged into Tiamut, and houses my old characters in their 20's and 30's. Wanting to start over and learn the game again, I rerolled a character on the new server and got to about level 15. 

Now I need to decide which server to continue on with. Zharun seems nice with the influx of lower level people, but this would mean leaving my other chars behind and starting on a server where Abyss fort sieging still seems to not be happening very often. Tiamut on the other hand seems the exact opposite, and I am worried that I will not see many people to do dungeons and such with as I level. 

So basically looking for input from people who have experienced the two servers and can give some insight onto which server I should continue on with. Tried browing through Aion's forums and found really no insight into the matter. 

Thanks in advance.