Though I'm not sure what the limit is, I play on Siel server at Aion Classic. It's very full both in the day and at night (I'm NA East). It's a lot of fun, and it's highly populated with EU as well as NA players. I would recommend joining us. :
After a closer investigation i would not be joining the team, mainly due to the nature of the company behind aion. It will take me too long to catch up, i'm not an expert, and it will be an absolute nightmare to be successful.
The Elyos are also cause of grief for Asmodians in Heiron. Some even are known to gank those who are farming Aether over a gate. I mean if you got an advantage, why not take it.
Retail turned out to be an entirely different game. Anything you played with as a kid is still there, and I wouldn't recommend it. I've covered the most significant distinctions in my post history if you're interested in the changes that occurred.
Classic is a good option, but since there are only two servers, they are still balancing out. Siel is more pop-oriented and asmodian-heavy, and they have the majority of the space. This means it is difficult for them to get AP occasionally.
Israphel is lower in pop and more heavy on elyos, they own approximately 50% of the abyss with the remainder of the 50% being split between asmo and balaur, making it much easier to mine AP. NA But I only have played during EU times. Although it can be quiet at times but I've never had any issues getting groups.
To be honest, Israphel's dead. AP farming is easier since forts are open. However the same 5-6 players will be on the job continuously to farm guards which makes it hard to earn AP at lvl 45+.
That's why I'm trying to bring some life back into the world. There are at the very least forts to capture/lose. The only thing I know about Siel is that the asmos have an iron hold on them and will not allow anyone to go back and recap.
If that weren't evidence enough, there are individuals who have been found to have been unbanned for having been flagged as falsely indicating that they turned several times in the course of a single event. NCSoft shouldn't ban just one or two people, and then ban all others.
This is the only question you can truly answer. What are the other rewards that players receive when they return to an open game? This is the kind of quest that individuals do. They go in, kill mobs and get quest items. Then, they leave (through one of the many options of exits the game offers) before turning it back in to accept the next repeatable, then entering ....all within the identical scenario. And those mobs that they killed previously? They're dead and no longer there. They aren't going to respawn which means that no loot is possible. This has been happening for years, but suddenly it's not allowed? It's ridiculous! It is absurd.
If you want to buy it, you can access https://www.mmoexp.com/Aion-classic/Kinah.html