It is probably your CC, if must not have Auto Face, or has Auto Face turned off. What CC are you using?
It has Autoface enabled. Right now its using singular. I tried 2 other ccs before, same issue, randomly runs through pack of mobs, stands still on mount, gets hit. Wont turn around to hit them. Works fine in BG tho
Depends on the routine your using. Most routines you can disable/enable target facing and just targeting in that manner. So the answer is No, its not common. You just have the setttings wrong =)
Settings arent wrong if it works just fine in BGs, but in terms of questing it can randomly pull a bunch of mobs and not do anything abouti t.