B1-> Nayat is too random to be punishing. This could be changed by keeping the buffs random but needing to KILL the guardians one by one. They then drop a box, where the event then would be playable. If more than one Guardian is killed at a time, the previous box disappears. This would put the flow of the fight into the hands of the players and allow for punishment.
B3-> Perhaps a secondary tank should/could be neccessary here? One to tank the worms and one to keep the boss. Could tie in nicely with Boss 1. Perhaps let the stomach acid recude defense by 5% each in addition to the %-DoT, so that a 20 debuff leaves one with 0 def.
B4-> I would personally put some emphasis on the adds that come; they could be attackable, so that one may need to pull them away from the group to avoid a new debuff (perhaps, like, 50% less damage/heal dealt for 2 seconds).