I had the same problem in 10.10.2 (Yosemite). Here’s what I did: Open EZDrummer 2; Go up top to Settings; Click Audio/Midi Setup;
MAKE SURE YOUR PLUG IN WHATEVER USB MIDI CONTROLLER YOU ARE USING TO TRIGGER THE SOUNDS.
Make these Selections: Device type: CORE Audio; Output Device (Your DAW Card connected to your computer; Buffer size 256;
Out Channels: Click Multi Out; then select: Output 1 – Output 2; Output 1 – Output 2; Output 1 – Output 2 (for all 3 L-R Channel Outputs)
CLICK MIDI DEVICE: Select your MIDI Controller (check the box)
Go to MIDI Channel: Select MIDI Channel 1.
Open a new session in Pro Tools; Go to Track; Create a new track; Select Stereo Instrumental Track
Select the Instrumental Track; then Track Enable (click the record track function.
Move across to inserts A-E in Pro Tools; Click the first tab (top tab)
Scroll to instrument in the tab, click instrument, scroll down and Whoop There it is: EZ Drummer 2.
Hit your controller and you will hear the drums and see them move.
I am enjoying it right now, I just bought it last night. Let me know how you make out with this.