ISP/Internet Connection cuts out randomly on Mac

Hi all.

I'm having a frustrating time with my Uverse internet lately and hope someone here can give me some tips to get back on track.  The situation is this:

- Mac Pro, running Yosemite, connecting via WiFi to NVG589

- Connection has been stable for over a year, then has suddenly become attrocious.  The WiFi remains stable and strong to the router, but I am constantly dropping the connection to ISP and Internet.  Sometimes connection will remain stable for hours, sometimes will conk out every few minutes.  This info from the mac's Network Diagnostics panel.

- This is occuring ONLY on the Mac Pro.  Other devices continue to connect to internet successfully.  Neither the mac nor the router have moved nor had any odd interference adding things added.

- Restarts generally solve the problem for a short while.

I've changed DNS servers a couple of times.  Changed every setting a couple of times.  So I'm now totally lost.  What should the DNS be?  Is there some other issue?

Up until now, what had worked well was setting the Network to "Link Local Only" and using Open DNS.  currently I just now set it to Google, and I have 4 dns addresses in the list in this order:  2001:4860:4860::8888, 8.8.8.8, 8.8.4.4, 2001:4860:4860:8844

Search domain is set to attlocal.net.

The settings on the router are, I think, all set to default after the most recent restarts.

Currently, right now, my internet is up.  Over the past hour I was watching the network status and the ISP/Internet connection would cut out literally every minute, then pop back on, then cut out.  Now, inexplicably, its up and running perfectly, pages loading like lightning.

Do I have a software conflict somewhere?  a gremlin?  skynet?  what?

Any ideas on what to look for and how to troubleshoot would be welcome.  Perhaps it will all stay stable now by magic, but I would like to hear from other Mac users and what their setups are.  Thanks!