I will keep this short. One of two things should happen. Either they need to increase the re-spawn time just a bit (30 seconds to a minute) or the better solution, make is so you have to press a button to activate the respawn.
There are two big problems. First, any pet build is a nightmare to test with. Once you finish the test, you have to (within about 1.5 seconds) remove the skill from yourbar to cause the pet to despawn, or it just starts attacking the same dummy again. It is really frustrating in practice, because usually I have to do a test and then kill it a second time so I have a clean dummy to test again.
Second, (and thinking about ZOS's wallet), I would love to be able to place multiple dummies together to test AOE. Now, there is no point because they just continue to respawn as they die, which means you cant get as solid parse out of it unless you magically kill them all at the same time.
Carry on.