one of these guys coned even to my levl 15 wizard they hit hard and several times i had to cast root before it worked even though i have an 80 in alteration after that my shock of lightning did only 5 damage one time it always does 81 be careful these can be hazardous to any casters helth when you get jumped by one.
Just for the record, Blue does not mean that the MOb is one level below you, that is a misconception from the newbie levels, it means that it is anywhere from 1 to 4 (or 5) levels below you. Thats why not all blues give the same exp.
These guys con blue at level 15, but they hit fairly hard, very quickly. Made it impossible for me to cast and my Bard partner kept missing notes in her songs.