Here were my strats for what I've done so far:

Echo of Baine:

This is a DPS race, so I popped hero pretty early.
Put all toons on follow and blast boss at the edge of a platform near another platform to swim to. if a ranged DPS gets blasted off, swim him over to the next platform. Just cycle through the platforms.

Echo of Jaina:

Slaves at range (all my dps is ranged), and blast Jaina...When she does the frost blades, put all on follow to avoid them. When she does the flarecore, switch to that...rinse and repeat.

Murozond:

He does surprisingly little damage directly. I just put all slaves on follow and dps. Each time he marks for the bomb, move aside. You can pretty well kite him around for a while. Unfortunately you'll eat the breath, but it is heal-able. Use your tank on the hourglass last. Make sure you always leave a path for a slave to run off to the hour glass. Make sure that the initial positioning for the pull is the most convenient to immediately resume DPS on the boss. I found that follow works very well but it makes the fight take a bit longer.