Good starting point is to have everybody in your raid group run torparse or parsec. Numbers don't lie. You can see who has the weakest dps, who has the most ehps, how much damage tanks are taking and from what source, and more stuff like that. Parses are a great way for you to dissect the fight bit by bit, and are always the best starting point to see how each individual in a raid performed.
not standing in red circles while yelling at others to get out of that same red circle is also a good thing, not mentioning any names.
and on a more serious note, its hard to tell whats happening without log files, but it seems you left thundering blast on cd too much and hardcasted cl at least once.