Im not surprised. Its LFR. You're lucky as is to have everyone there and not afk on the fight, let alone people actually caring enough to play their class right. The vast majority of players in LFR just don't care. They don't know their class, wont learn their class, and don't care if they die or not on the boss. Determination only helped that because now if they die, they will just get a buff so they can care even less. LFR is sadly not the place where mechanics can be around. There are just too many people in the group. You cannot possibly pick out all the slackers and remove them. Especially when it takes so many people agreeing to do so.