For Cadence - there really seems to be two issues going on. 1.) is a slow increase in lag throughout the week that is usually at it's worst on Monday evening before server maintenance on Tuesday morning (talking US time here). This seems much better recently. 2.) is revolving around major events with lots of players. 6 weeks ago, it was getting really bad right before a rift or public slaying - more recently it seems good right up until the boss dies, then within a minute or two the lag sets in and catseyes, waypoints and even bridges do not load until too late. If you need to "watch" it happening - one of these events - even Dev hosted - might make for a great stress test.
I kind of assumed the first might be a memory leak slowly accumulating over time through the week - then cleared with server maintenance to cycle again.