Speaking as a player that's cleared all the extremes several times, I've actually noticed random lag spikes as well. Something is up after the recent patch-- I never had rubberbanding issues before (like ever) but it started to happen a lot in pvp and the extremes. Coil seemed alright this week (cleared turn 5 without spikes) but I did notice some weird visual lag at random intervals when we were doing the primals afterward. It occasionally got me killed.

I'm sure 99% of the time people claim a lag spike, they just messed up. But-- at least lately-- there's something strange going on with visual lag in the game. And I'm in the U.S, NY, with Verizon Fios.