Yes, seen this so much. Had one today in Toto-Rak. They kept using shield bash and just concentrated on the one mob. They would occasionally cast Flash when we were running to the next pack. Made no attempt to pull threat from anyone. Was very annoying, eventually just had to Abandon Duty as we couldn't get past the second boss. Tried to interact with them, I even asked if they were human, no response. Not the first time I've experienced this... :P