Can say I've only grouped with maybe 2 good bards, the problem is alot of bards will mez adds that are easier/more efficient, IE the ones at the front that are easily targetted or the ones hitting him that make him auto target. I'm not saying it shouldn't be done this way, but the few good bards that i grouped with reacted to the pet and the owner, not mezzing a mob that is already engaged and therefore messing with DPS of the pet and it's magician/necro owner. But I realize alot of the time when u need mez, it's a clusterfuck, and people's health are dropping so u just need to get shit mezzed, so to that I say, yes every pet class should know what to do in that situation, be it rooting as a necro, or backing off and reapplying the pet elsewhere as a mage.