I suspect that there are multiple, and confounding at times factors. I never have lag, even in the 'Moors in a RvR (on Nimrodel ... can't say anything about Dwarrowdelf because I have not gone to the 'Moors there) unless my ISP is having problems (which is often). I don't have to have the ping go 'off the charts' for it to happen. I simply need the dropped packets happen strategically (such as the chat server connection having trouble).
A recent problem showed backbone trouble to be the bottleneck, such that my ISP had to change backbone providers to route around it. It wasn't enough to adversely affect my ping that much. It was apparently when and what got lost and how quickly the re-transmission could sync up.
That said, if client performance issues do get fixed, that should help everyone most of the time (but it won't help all of the time).
"No sadder words of tongue or pen are the words: 'Might have been'." -- John Greenleaf Whittier
"Do or do not. There is no try." -- Yoda
Indeed, in a world and life full of change, the only constant is human nature (A is A, after all :P).
We old vets need to keep in mind those who come after us.