I had bad lag in Cyri primetime zergfest, sound drop out, unplayable in high mob density content such as Maelstrom and vet anything.
I upgraded my machine to an i7 6700k with a Gigabyte gaming 6 board. The board has a "game specific" NIC setup. I kept my HD7800 vid card for now.
I had figured most of the issues were on my end as my old cpu was pinned or close to it a fair amount, I hadnt realized how much my old network gear and setting were having an impact.
I had upgraded my connection from 5Mb down to 35Mb down and installed a new NIC in my old box but never saw more than 3-5Mb down.
On the new gear I'm seeing d/l speeds of 28-30Mb on steam and the lag in ESO has disappeared in all but primetime zergfest. All high mob density content is now playable and I now longer have sound dropout of any kind.
I see 80-100fps on high quality no shadows/reflection with drops into the 40's during combat. Again zergballs drop me into the low double digits but it's better than the 1-3fps slideshow I was seeing.
I cant wait to get my new vid card
Even if you have quality gear you may not have optimized nework settings.