For the lag you are experiencing during the Kaalgrontiid campaign, you can try the troubleshooting steps here which may improve your latency.
new patch has done nothing to combat the cyrodil latency issues. I am experiencing lag so bad that I have to spam an ability 6 to 10 times for it to fire. I just fought in a few 1v1s where one ability from each of us would fire every 5 seconds -- forget about defense and skill... just spam 1 ability and maybe it will go off.
How is this considered okay?
For the lag you are experiencing during the Kaalgrontiid campaign, you can try the troubleshooting steps here which may improve your latency.