Maybe you noticed, maybe not but scrolling in Office (Excel, Word...) doesn't show the content on Windows server 2012R2 with XenDesktop/XenApp 7.x This can be quite annoying and took some time to find out that Citrix is the reason for it!
With Windows Server 2012R2 the Windows performance settings is not only the value of the VirtualFX key, it's set mainly to the UserPerferanceMask registry key. If you are missing some setting, then Office will not show the content while scrolling (might still work with other apps). Using progmon you will find that Citrix wfshell is changing the value during logon in a way that users basically have just ticked three settings in the preference!
Searching the Citrix KB you will find a Hotifx ICATS760WX64034 that you need to install and set the following registry key:
EnableVisualEffect REG_DWORD = 1
Problem solved? Hm, NO! This hotfix cannot be applied to the latest VDA Agent 7.6.300 and is also not included! Someone at Citrix forgot to check in the fix for the next release! There is no Hotfix available at the moment. You could use just the wfshell from the hotfix and works but you never know what other issues you might get doing so. So I'm NOT advising you to do it.
Update: Citrix messed up the registry value with the 7.6.300 VDA and you actually need to set the value
EnableVisualEffect to "0" instead of "1"