I determine that it was DNS related the same way as you did, by pinging a IP address.
If you have not already done so, you can see the step I took to get wifi working in 17.04 by following this link
https://ubuntu-mate.community/t/wifi-issue-in-17-04/12622/15?u=steven
There are two links in that post that may be helpful to you also.
The issues some of us are experiencing with WiFi in 17.04 are Ubuntu specific. All flavors are affected, not just Ubuntu Mate, as you saw when upgrading xubuntu 16.10 to 17.04.
What is there to do then?
I'm the kind of a person that likes to fix things. The part of computing that I most enjoy is installing and setting up operating systems. After I have one installed, tweaked to my liking, and everything is working well, all that is left to do is use it for everyday task, which honestly I find to be a bit boring.
I installed Ubuntu Mate 17.04 Beta 2 in hopes that there would be things that did not work so I would have a opportunity to fix them. However, I installed Beta 2 on a spare laptop. The laptop that I depend on is running Ubuntu Mate 16.04 LTS, and it will be until I upgrade it to Ubuntu Mate 18.04 LTS.
My point is that on any computer that one has to rely on, the best practice is to use the most stable version of your chosen operating system. In the case of Ubuntu that version is the LTS releases in my opinion.
So unless there is a specific reason you need to use a newer version, I would recommend you try a Ubuntu Mate 16.04 LTS live DVD or USB. Chances are it will work better for you than a newer version. If it works well with your hardware, then you can install it and have a stable operating system that has no need to be upgraded until the next LTS version is released.
Unless of course your are just using 17.04 as a learning opportunity as I am 
Some links you might enjoy
https://www.ubuntu.com/info/release-end-of-life
https://wiki.ubuntu.com/Releases?_ga=1.64771046.815780011.1492318950