I started soloing these at 51 - at that point i think they were all red to me. Use your little 10 damage root spell instead of your latest one because they break root so often (no matter what root you use) that you can save on mana using the lower level one. At 51 it took me about 25 minutes to kill one because they have so many hps. Once I got ES vambraces it went a tiny bit quicker. After I got winged death at 53 it took me about 15 minutes to kite one. Without KEI for me it's not possible because I don't have uber gear. Hope that helps :)
Crys