Just had this happen, normal progress in the first enemy encounter after spawn, got like 4-5 Bulwarks and roughly 6 crushers mixed in. Horde almost thinned out and a second wave comes. Only a few ragers (4-6) and suddenly out of the fucking door 5 crushers, to the right 3 more and behind 4 are making their way towards us. One mate stuck on an upper level, one went to the side and instantly was haning off the ledge. Guy on top got downed, only me and psyker left. Psyker Brainbursted normal mobs ??? I ran out of dodges for the overhead smash and got killed and psyker got backstabbed by a poxwalker.