We have updated the Anti-Xray plugin on the server so it runs much smoother, while still maintaining low false-positives. The anti-xray now has a field of view limit (it will now hide enemies behind the player no matter what), and we have also optimized the number of blocks that are checked. (It does a rigorous full check close to the observer as well as the target, but only checks a few blocks on the way between.)
The new system consumes less than 0.04ms average tick time between a pair of active players (around 4-5 times down from previously). This means that it will take at least 1250 such player pairs for the server to begin lagging – equivalent to a 25vs25 game (more than the max player limit in one game) where everyone is moving around (in reality many people stand still and that reduces the required amount of checks even further). This means that you can finally enjoy the server without any lag from the anti-xray system.