This may be a working alternative and you don't have to turn Origin in Game off (hopefully).
Install Afterburner & RiviaTuner package.
https://gaming.msi.com/features/afterburner
Set RiviaTuner's Application Detection Level = none ((this should allow it to work with Origin in Game))
In Afterburner's settings there should be a Screen Capture section you can setup.
---
I didn't test it (sorry) but that should work and Origin in Game can still be enabled.
That definitely looks interesting. I'll have to try it.
One of my friends told me about a program called lightshot where you can just press a button and it captures your whole desktop and saves it to a file. It's not as clean a solution as I'd like, since it captures all screens, but it seems to work with anything.
I'm still hoping someone will figure out how to get Steam working with GW2 though..
To answer this question I found steam overlay only worked when origin was closed, and I launched GW2 through steam, starting origin with it, if you set origin to close itself when exiting a game, you shouldn't have any problems again.
