Since the changes Dps really do need to hold back on aggro. Initial aggro (I'v Heard) is real bad for warriors and paladins, especially warriors needing to spread rend etc, most Dps can't wait or hold back. Death knights have never been better as tanks, long term threat in some cases is a little dicey but still not bad and druids are in a good position as well (judging by a friend of mine).
To any dps reading this, unless you can transfer threat or drop threat real fast, hold it back. please.