There was a change to how world drops are done. Currently the default world drop is health and magic pots (a world drop, for those that don't know, is a drop that is added to every mob's drop table in a specific world). I changed how the drops are added to the loot table for mobs when making OA O3 not drop an OA key. Basically what happens is the current mob's loot table is checked to see if it already contains any of the world drops. Those found are removed, then the world drop added. In this way I was able to add the world drop of "Oryx's Arena Key" with a probability of 0 to effectively remove the key from OA. The side effect this had is that the health and magic drop percentage has decreased since a mobs loot table can not have duplicates of the world drop.
As for the lag, it is hard to pin down an exact cause. We've recently moved to another server (same stats as before 8 core, 16gb memory). This was done to get a clean working environment again (much like when one decides to wipe their computer and start clean). That might be one reason. We also have what should be a minor increase in work load on the server due to an extra program running on it (ydg). This too should not cause much of a difference. Something else that was changed, communication between the server and your client is now encrypted. That adds a little overhead which impact isn't quite clear. The actual server doesn't process much more than it has before but communication though. The TL;DR; of it is I really don't know atm. It will be something we look at in the future.