You forget that most DPS people know their limits of what can and can't be done in an exp group to keep agro on the MT. They don't want agro as much as you don't want them to have agro.
This guy in my example was a recent betrayer to assassin. He was playing, since everything we were fighting was green and no real danger. Despite my best effort, spamming every taunt I had, even switching to offensive and putting on my dps gear to try that way, he was able to pull agro on every fight. Because he WANTED it. So yes, if a dps wants agro bad enough, they can take it. Even if you are "on" that night.