It is known in-game that using the same weapon as your companion against the same target boots the damage delivered. However targeting can be screwy at times, especially in the heat of battle. Is there a button I can press to "auto-lock" or synchronize my characters target with that of my companion(s)?
I wish too that there have a button to synchronize my target with that of my companions, but I think that there are not!
Otherwise, to lock a target, just press L1 (PS3).