Merc questionFollow

I never used mercs before but what does setting someone up as Main Assist, Puller or Tank do to merc reactions?

For those that dont find the answer, you can't make the merc the main assist or puller, those have to be human players. (At least today they do.) If you molo setting yourself as puller means the merc wont follow you he stays in a spot and you bring the mob in. The merc will aggro when you are close. You may have to take yourself off puller to reposition the merc every once in a while.