new Comcast customer HORRIBLE coverage

We're a new comcast customer and we went with the xFi gigabit connection with the advantage addon so we could get the mesh pods.  On installation day I was told Comcast needs to run an assessment to get them to me.  Since then, i've had horrendously slow wifi speeds anywhere but my main room.  Wired in I can get reasonably close to the max speed, but in my office which is probably 50-60 feet I can only get wireless N speeds at about 30mbps on my AC built in Wireless card.  I went out and bought a new AX card for my PC, still only gets wireless N.  I confirmed with my mac laptop again only gets N speeds.  So I hooked up my own Asus Tri Band AC router in repeater mode and can get a solid sustained 200mbits speed (20% of my total . Then I tried a TPLink 2000mbps power line networking adapter and well, that was a waste as well.  

So currnetly I'm using my own ASUS router as a range extender to make a DIY mesh for my office.  But other areas in my house are poor N connections as well (my deck outside, maby 25 feet from the xfi router bounces between 2.4ghz N and a really slow AC connection), my wife's office upstairs is the same way.  

I can rig another router to handle the upstairs but i haven't heard anyhting about any assessments or even how to check the status of it, but with all my DIY stuff to make my internet functional I'm concerned it's going to create an issue with the assessment.

Also, when the installer was here they couldn't determine where the amp was connecting to in the basement, so they hardwired into an outlet on the main flor (which is fine), but I don't beleive i can move the xfi router anywhere but it's current location.