LOL i would say no merc period, cause if you use a zon all the sorc has to do is grab a merc thats under lvl 9 and she will take almost all the hits for you... and wont get hit nearly as much.
Usually I like it when the sorc uses a merc, she wil think she is invunerable and just tele like mad... 1 good timed ww and its over for her.. and her merc.
Man i have a Wf and 2 white rings...I don't have to worry about the sorcs' attacks so i just multi like mad... the merc usually doesn't stay alive that long. Then i GA the sorc )
when the sorc uses a1 merc you just have to live long enough to let the rogue move shoot her and redirect your shots back at the sorc. if they are from a2 you usually only have to worry if they teleport directly on top of you in which case they can probably kill you quickly with alot of physical and elemental damage