Thief, Necro, Ele, Rev (Has to have a target), Guard (Has to have a target), Mes... (Don't think i'm missing any) can all teleport or shadowstep (Whichever term you prefer) up/through cliffs, not just Thieves. Thieves are generally a get in and then GTFO playstyle class because if you can actually pin one, they're squishy. Necro has plenty of AoE/pressure skills and conditions to be able to deal with a Thief but if said Thief wants to get away from you, not much your going to be able to do about it...