Also experiencing this on a Thinkpad T530 running Arch with kernel 3.11.6.

00:02.0 VGA compatible controller: Intel Corporation 3rd Gen Core processor Graphics Controller (rev 09) (prog-if 00 [VGA controller])
        Subsystem: Lenovo Device 21f5
        Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx+
        Status: Cap+ 66MHz- UDF- FastB2B+ ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
        Latency: 0
        Interrupt: pin A routed to IRQ 47
        Region 0: Memory at f1400000 (64-bit, non-prefetchable) [size=4M]
        Region 2: Memory at e0000000 (64-bit, prefetchable) [size=256M]
        Region 4: I/O ports at 5000 [size=64]
        Expansion ROM at <unassigned> [disabled]
        Capabilities: <access denied>
        Kernel driver in use: i915
        Kernel modules: i915
 
01:00.0 VGA compatible controller: NVIDIA Corporation GF108M [NVS 5400M] (rev a1) (prog-if 00 [VGA controller])
        Subsystem: Lenovo Device 21f5
        Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx-
        Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
        Latency: 0, Cache Line Size: 64 bytes
        Interrupt: pin A routed to IRQ 16
        Region 0: Memory at f0000000 (32-bit, non-prefetchable) [size=16M]
        Region 1: Memory at c0000000 (64-bit, prefetchable) [size=256M]
        Region 3: Memory at d0000000 (64-bit, prefetchable) [size=32M]
        Region 5: I/O ports at 4000 [size=128]
        Expansion ROM at f1000000 [disabled] [size=512K]
        Capabilities: <access denied>
        Kernel driver in use: nouveau
        Kernel modules: nouveau

Try updating your intel ddx -- nouveau is not responsible for the contents of the images it renders when in reverse-prime mode -- the primary gpu is (in your case, intel).

Getting what appears to be a less-serious version of this bug on Debian Testing with the Intel driver from Experimental (2:2.99.916+git20141119-1~exp1).

I'm also using a W530, in Optimus mode in BIOS.  

Dragging windows around the DVI/DFP display leaves artifacts and tears.  The internal display (LVDS1) looks fine.  Scrolling and typing is similarly slow; gnome-terminal is particularly ugly

$ uname -a
Linux dtp 3.16.0-4-amd64 #1 SMP Debian 3.16.7-2 (2014-11-06) x86_64 GNU/Linux

$ lspci | grep -i VGA
00:02.0 VGA compatible controller: Intel Corporation 3rd Gen Core processor Graphics Controller (rev 09)
01:00.0 VGA compatible controller: NVIDIA Corporation GK107GLM [Quadro K1000M] (rev a1)

$ xrandr --listproviders
Providers: number : 2
Provider 0: id: 0xae cap: 0xb, Source Output, Sink Output, Sink Offload crtcs: 4 outputs: 3 associated providers: 1 name:Intel
Provider 1: id: 0x68 cap: 0x7, Source Output, Sink Output, Source Offload crtcs: 4 outputs: 5 associated providers: 1 name:nouveau

$ xrandr -q
Screen 0: minimum 8 x 8, current 1920 x 2280, maximum 32767 x 32767
LVDS1 connected primary 1920x1080+0+1200 (normal left inverted right x axis y axis) 344mm x 193mm
   1920x1080     60.00*+  59.93    50.00  
   1680x1050     59.95    59.88  
   1600x1024     60.17  
   1400x1050     59.98  
   1280x1024     60.02  
   1440x900      59.89  
   1280x960      60.00  
   1360x768      59.80    59.96  
   1152x864      60.00  
   1024x768      60.00  
   800x600       60.32    56.25  
   640x480       59.94  
VGA1 disconnected (normal left inverted right x axis y axis)
VIRTUAL1 disconnected (normal left inverted right x axis y axis)
LVDS-1-2 disconnected (normal left inverted right x axis y axis)
VGA-1-2 disconnected (normal left inverted right x axis y axis)
DP-1-1 disconnected (normal left inverted right x axis y axis)
DP-1-2 disconnected (normal left inverted right x axis y axis)
DP-1-3 connected 1920x1200+0+0 (normal left inverted right x axis y axis) 518mm x 324mm
   1920x1200     59.95*+
   1920x1080     50.00  
   1600x1200     60.00  
   1680x1050     59.88  
   1280x1024     75.02    60.02  
   1440x900      74.98    59.90  
   1280x960      60.00  
   1280x800      59.91  
   1152x864      75.00  
   1280x720      60.00    50.00    59.94  
   1024x768      75.08    70.07    60.00  
   832x624       74.55  
   800x600       72.19    75.00    60.32    56.25  
   720x576       50.00  
   720x480       60.00    59.94  
   640x480       75.00    72.81    66.67    60.00    59.94  
   720x400       70.08  
  1680x1050 (0x6c) 119.000MHz
        h: width  1680 start 1728 end 1760 total 1840 skew    0 clock  64.67KHz
        v: height 1050 start 1053 end 1059 total 1080           clock  59.88Hz
  1280x1024 (0x6e) 108.000MHz
        h: width  1280 start 1328 end 1440 total 1688 skew    0 clock  63.98KHz
        v: height 1024 start 1025 end 1028 total 1066           clock  60.02Hz
  1280x960 (0x71) 108.000MHz
        h: width  1280 start 1376 end 1488 total 1800 skew    0 clock  60.00KHz
        v: height  960 start  961 end  964 total 1000           clock  60.00Hz
  1024x768 (0x79) 65.000MHz
        h: width  1024 start 1048 end 1184 total 1344 skew    0 clock  48.36KHz
        v: height  768 start  771 end  777 total  806           clock  60.00Hz
  800x600 (0x7d) 40.000MHz
        h: width   800 start  840 end  968 total 1056 skew    0 clock  37.88KHz
        v: height  600 start  601 end  605 total  628           clock  60.32Hz
  800x600 (0x7e) 36.000MHz
        h: width   800 start  824 end  896 total 1024 skew    0 clock  35.16KHz
        v: height  600 start  601 end  603 total  625           clock  56.25Hz
  640x480 (0x86) 25.175MHz
        h: width   640 start  656 end  752 total  800 skew    0 clock  31.47KHz
        v: height  480 start  490 end  492 total  525           clock  59.94Hz

Original reporter hasn't responded since 2014 -> https://bugs.launchpad.net/ubuntu/+source/xserver-xorg-video-intel/+bug/1228506/comments/19 .