Heres the situation!
You are a warlock in full epics in a random heroic. You have DI. Somebody tells you to use it. You've got into a group with a moonkin, rogue, resto druid, and dk tank.
Do you put DI on:
A) The DK
B) Your pet
C) Other and why
Would you get upset by the dps loss your pet would have without DI in the random? It didn't bother us too much, we were all pulling 20k+ dps and he was pulling a good 15k, but WHY would you do that. Surely it's a dps increase for him too to have a better dot increase uptime lol.