Its just a practice thing, really - the first time you do CM or the other pre-end-game dungeons its going to be a little shaky as you learn where things spawn, etc.

It will depend on your group too..if you cannot get the mobs wrangled before they murder a WHM healing the tank, that's your problem and you just need some more practice : D. If you can't keep the mobs off 5 dps dpsing 5 different mobs, you can't do much about it - just try to focus on getting the attention of anything going after healers, really squishy dps, or the other tank.

Obviously if you can perfectly execute, take aggro from all 6 mobs and keep them the whole time, you are awesome - but its not always possible. Flash>CoS>Flash>SW>Flash>Flash>Flash>Flash will NOT keep aggro over a bard going full bore on a single one of those targets if they are at least as geared as you, its just the way of the world.

PS I would not use the main enmity combo while you have at least 80% of mobs in range of flash and you still have MP. If a mob gets loose go Provoke+Shield Lob then go back to flashing. Specifically on this fight, use Riot Blade combo to get your MP back between add spawns.