"I have a Roland TDK11 kit. Curious to know how you are able to monitor your Yamaha’s brain while tracking. Are you recording Yamaha output (audio? Midi?) along with other tracks in Sonar? How do you listen to both Sonar output AND direct monitor your Yamaha at the same time? I’m midi-triggering Addictive Drums 2 via a Focusrite 2i4."
 
I don't know how Cactus does it, but I monitor all my MIDI instruments through a mixer.
Audio output of instruments is plugged into the mixer. Audio output of the interface is plugged into the mixer, too.

Of course! The answer is right in front of my face: my 8-channel Yamaha mixer. Doh!

Thanks for the brain jog. Must be lack of coffee. 😳

I am a Noob, so I can play on TD-11 with AD2, even with audio output throw TD-11 (build-in Edirol). The last option is not really convenient, a bit too much latency. But throw "real" audio interface, it is ok for me.
 
When I had one of that "WT... is going on?" moments with MIDI latency, a friend was visiting me. He (also hobbyist) has not played with AD2 before, so I have switched on my system. He has tried with the conclusion "sorry man, but that is no playable...". I have tried myself - really "no go".  I have turned on my DP and I could barely play it with TruePiano. I can play slow peaces with up to 30ms latency, but this time it was more. I took my MPK mini and surprise, the latency is as usual. I had no time for investigations, so I have turned the system off. Later, after turning it on again, everything was working properly again.
 
I am a kind of unlucky with music setups. Strange things happened exactly at times when that was more or less critical. Like continuously crashing with my notebook VS-20, after 2 days working fine and just several hours before I had to use the setup (that can be called lucky moment, that has forced me to buy RME which was a good move). Sonar has reverted to demo mode in the middle of video tutorial recording (which I do not do often). MIDI latency, when someone is visiting me. Etc.