It appears that the aside from Blizzard, the recently merged vanilla server, Elysium Project, is suffering from other external issues following its official launching. Here's the recap of what happened to the server for the past 72 hours.
DDoS Attack
DDoS attacks are not uncommon in the world of MMOs but private servers are more susceptible to these attacks and Elysium isn't an exemption. Since its official launching, the server has been constantly bombarded by DDoS attacks which virtually rendered the game unplayable. This led to frequent down-times and maintenance but yesterday, the team finally managed to stabilize the server and is now back online.
Population Cap
Nostalrius and Elysium are among the largest vanilla private servers in the past and with the recent merge, the spike in population certainly affected the host server. Added to this is the server's growing popularity due to its issues with Blizzard which inadvertently polarized some of its subscribers. Now, the server is swelling dramatically which led to the developers limiting the population cap of the PvP server to 9.5k. This resulted to longer queues and whatnot which can be seen on this Reddit thread.
System Performance
Despite the pop cap, the server is still experiencing severe lag and bug issues which are affecting the experience of many players especially for those that are in the PvP realm. Developers are constantly running maintenance and updates for the server which can be observed on their official Twitter account. As of the time of this writing, the server is now back online after a short 30-minute maintenance.
Transfer and Ban Issues
Elysium Proejct recently issued a huge ban wave after several players trying to exploit some glitches and other illicit acts which violated the server's Terms & Conditions. The move however, also caused some "innocent" players to flood the game's customer service which was addressed on this tweet. Aside from this, Elysium Project has its hands full on players that were not able to login to their previous accounts or in some cases, had some of their items missing on their inventory.
It's clear that the developers still have a long way to go in order to stabilize the whole server but we may be seeing all of their efforts gone to waste when Blizzard finally speaks up on their stand regarding on establishing private servers - which is, without a doubt, illegal in every manner.