Thank you guys for the helpfull feedback. While it was by no means an optimal raid for any of us (19 ppl signed at start, some of our best people had to go in 2nd spec to fill out gaps), hopefully tomorrows raid will be better (28 signed).
I will take your advice and deal with the situation. djuni will most likely not be staying as she is on trial and not performing. Matas and shardless will get a warning and if they fail to improve to a acceptable level (taking into account the missing caster buffs) they will be demoted.
Appart from to low dps, all our locks suffer from just plain beeing dead. I guess when they died in fires half the time I should have just removed them then. But everyone always gave me excuses like "cloth dps die really easy in wotlk" etc etc.
I think when all 3 locks had SS on themself and died twice during faction champs and these were the only 6 deaths during the fight was when it just went too far..