I'm using debian jessie+backports with thinkpad W500 (gpu Intel@GB45 + Radeon firegl v5700), to enable DRI3 i compiled intel+ati driver download from jessie backports sources, and config /etc/X11/xorg.conf.d/10-gpu.conf is:

Section "ServerLayout"
    Identifier     "Layout0"
    Screen        0  "Screen0" 0 0
    Screen        1  "Screen1" LeftOf "Screen0"
EndSection

Section "Monitor"
    Identifier     "Monitor0"
EndSection

Section "Device"
   Identifier  "intelGPU"
   Driver      "intel"
   BusID      "PCI:0:2:0"
   Screen     0
   Option     "DRI"  "3"
EndSection

Section "Device"
   Identifier  "radeonGPU"
   Driver      "radeon"
   BusID      "PCI:1:0:0"
   Screen     1
   Option     "DRI"  "3"
EndSection

Section "Screen"
    Identifier     "Screen0"
    Device         "intelGPU"
    Monitor        "Monitor0"
EndSection

Section "Screen"
    Identifier     "Screen1"
    Device         "radeonGPU"
    Monitor        "Monitor0"
EndSection

I can logon trinity tde(kde3) desktop and run other things ok. Just testing any 3D game (such as Titan Quest Immortal Throne) with wine1.9(without nine adapter patch) + DRI_PRIME=1 i got game window tearing,flicker, fps nearly about 70% of using single radeon card. 

Test same games with single card (intel or radeon gpu) booting, game window dont show up tearing,flicker.

Logon desktop with switchable dual card, i got some information with some check:
 
#grep EE /var/log/Xorg.0.log
[    13.354] (EE) Screen 1 deleted because of no matching config section.

#more /sys/kernel/debug/vgaswitcheroo/switch
0:IGD:+:Pwr:0000:00:02.0
1:DIS: :DynOff:0000:01:00.0

#xrandr --listproviders
Providers: number : 2
Provider 0: id: 0x78 cap: 0xb, Source Output, Sink Output, Sink Offload crtcs: 3 outputs: 4 associated providers: 0 name:Intel
Provider 1: id: 0x51 cap: 0xf, Source Output, Sink Output, Source Offload, Sink Offload crtcs: 1 outputs: 1 associated providers: 0 name:radeon


I also tried enalbe intel+radeon TearFree option, radeon glamor option, or without any self xorg configure just totally automatic config (intel dri3+radeon dri2), and using wine staging 1.9.3 binary deb, also show up the same problem that make games unplayable particularly eating video card games.

I'm not sure what cause the problem. Does mesa dri_prime way exists some bugs, or it's wine bugs, or i miss something? 

Oh, 2D games looks good without the problem.

Thanks.