At that level you might not have any 'agro' gain abilities other than normal damage. The best you can do is make sure you are damaging all the enemies enough so they dont run after the rest of the group. Eventually you will get some 'threat gain' abilities and those will make it a bit easier. Also, keep in mind, it is the groups job to manage their own agro as well. If they are not targeting the correct enemy they can grab agro.