When you disable Application and Device Control in the SEP GUI by clicking on Change Settings > Configure Settings on the Client Management line > untick the option "Enable Application and Device Control" the printing is much faster.
The System Lockdown feature of Endpoint Protection may have been enabled recently in your environment by adding an MD5 hash to the blacklist on your Advanced Threat Protection (ATP) appliance.
Some processes not reacting well to the hooking of our Application and Device Control DLL.
- Check with Process Monitor for which process is taking the most CPU utilization during the printing task by checking the stack summary in Tools Stack\Summary. The Sysfer.dll may be taking up a lot of the CPU.