Same as Sonata...my blizz sorc can run the area easily, even on players 8. On /players 1 it's a cakewalk. Granted, your merc needs a high damage weapon to take out the Oblivion Knights. Mine uses an eth CV Insight, and for an added boost he's got Fortitude. Andariel's is recommended to hit an IAS breakpoint. Just teleport onto the OKs repeatedly until they go down. As the PvPers say...ez.
I recommend this build if you cannot afford a properly geared lite sorc.
CL/FO is my choice, best area clearer in general. Guide is in Sorc forum stickies.
Pure light is awful good too, but A) its expensive, and B) you can still occasionally get an LI/PI unbreakable Grand Vizier that will throw a wrench in your Chaos run.
CL/FO (with Infinity ideally, or Insight) has absolutely no unbreakable immunes, is much cheaper with full Tal's set than pure light is with HotO/CoH/Griffs, and FO is still superior to L/CL vs broken immunes (besides just being a useful area-clear skill in general). At solo player settings on bnet, you really dont need the extra 20 points in your L/CL synergy anyway, its overkill.
Plus, who wants to wait for Infinity to stick before you start killing those Storm Casters?