still no info about terror from beyond.
How many bosses?
Will there be another world boss as well?
Any novel mechanics?
Are they doing something original with trash mob?
Surely by now, bioware could share some informations?
How many bosses in a raid, to me is really dependent on the difficulty of the fights, and the loot that is being rewarded; usually though more is better then fewer, but if you start doing a large amount you need to give people the option to choose between bosses sometimes (aka. different wings).
For those who have played it, there was a boss event in karazhan, a wow raid instance, called the opera event. Each week, the game woud choose one encounter out of 3. So if nobody told you, you wouldn't be able to know what would be the encounter. I remember times where the raid lead explain the wizard of Oz and the Little Red Riding Hood would just appear (run away little girl, run away^^ )