Anytime I use any ability or cast a spell, it takes on average ~220ms before the ability starts. This delay can fluctuate wildly and waiting for example ~400ms after you’ve pressed a button before the cast bar even appears makes the game feel very unresponsive, not to mention the actual dps loss over longer fights. As a quick test i threw 10 frostbolts on a dummy while naked so 2sec per each cast, and it wasted 0.44sec (440ms) into the twisting nether. Thats a 2% dps loss right there, just from lag. And this is even with spellqueueing enabled at 400ms while chaincasting!
I made a ticket ingame but was also asked to make a forum post, so here it is.
Here’s a screenshot for illustration purposes, which shows the ingame latency in the tooltip to the bottom right, as well as the delay on the castbar itself.