I used to have the problems OP is describing... At launch. I lived in New York and they persisted up until I would say the time Haukke Manor HM came out, unless I played past Midnight EST then there would be no problems. It was clearly the route and as a result I had to either memorize the pattern and kind of linger around by myself, or use pingzapper. Pingzapper made it obvious it was the route. Then a month or so into the Haukke Manor patch everything cleared up pretty well, either due to my isp, SE, or the route itself improving on SE's behalf (of which they said they working on) for some time. Haven't been using Pingzapper at all since.

And I simply do not have the problems OP has for over a year now. I don't use cast bars as reaction. I don't use memorization-- I see the effect under my feet, and move. I can sometimes even be a pixel off at the very last moment and still not get hit, so I can't agree at all that it has anything to do with telegraphing the attack.