The first time or two you will find the instances difficult, but a few runs getting your attack sequence right it will be cakewalk. With 5 members I start instances at the lowest "recommended" level, sometimes I need a level or two to complete it, but rarely feel overwhelmed by trash. With 4 might want to wait till middle levels, YMMV. Your damage output will be high, 3 sheep, after a bit of practice you should stomp right on through.