I was going to write about how it is EA netcode and server etc. but I just experienced same thing. I have XBX with same router as OP. I have 1 gig dl/ul.
In game my ping shows 11 and static, but DumasOS shows it constantly changing between 16 to 29 to 40 to 50 within seconds. The VA server is the closest one to me about 300 miles away.