@MarcusJ1 

I never found a solution, I don't want a double Nat so I just live with it but it's annoying. I might just give in and hook the centurylink back up as a passthrough, which is stupid with fiber. 

@AdventureVia I also recently tried the TP Link C4000 router and TP Link AX3200 router. Both had faster internet speeds than the AX11000 when handling the pppoe and vlan tagging. It's a hardware issue which makes no sense since it's the highest end one they make. Thinking of returning it and maybe going with the Asus AX11000. 

I finally solved my issue. I turned QoS to standard (it was on gaming mode), turned off all homecare (not sure if that mattered) and removed all priority devices. My speeds are now at normal (above 900 up and down). Hope this works for others. 

@MarcusJ1 

never had those settings on and still have issues. 

That's really interesting that you were able to get normal speeds. I've never had those settings on though. Tried enabling and disabling them but no change. 

455 up 822 down

@AdventureVia One last thing, try manually setting the download and upload speed in the interface to 1000/1000. That might be the last missing thing. Someone else pointed out that this setting will basically disable the QoS. Also put QoS on "standard". Hopefuly this helps.

I'm having the same issue with upload speed as well. If tplink does not come with any solution, I will just return this to costco. :)

I'm at the return to Costco point as well. I've had it for quite awhile but no firmware updates have helped and TP-Link has never responded with assistance since my initial chat with them.