I can't be 100% sure, as it's been hard to get people to actually sit in the tower to test the theory, but if what we've been sayting is correct, actually everyone who uses DX11 does get the stutter, they either have gotten used to it and just assume it's just something they have to put up with or they assume it's their machine only.
The only way we're going to get it resolved is if enough people can do this simple test
Launch AH via the DX11 exe
When you appear in the tower, start a timer and open clipboard, right click / net status
You should see a spike at very close to the 10 min mark, wait 10 more mins and confirm you get another one (I'd wish for 3, but people got flying to do!)
Post back here and state you are getting the spike, or not (I suspect every DX11 user will)
If we get enough tests done, we might persuade HT to look at it, I think currently he thinks it's due to DX11 in terms of drivers or user machines, but I think it's that last hop for network traffic inside the HT network, it almost has to be, because SEA2 arena is not affected, you can fly all day in there on DX11 and never see a spike!