That is the question ;) .

Note that, at present, chain lightning (and normal lightning) are really slow, apparently using attack speed instead of cast speed or something. That might get fixed, though.

A socketed spear could do at most 60-84 damage with sapphires or 18-84 from Thuls. This damage is hardly worth mentioning, and a socket-only spear wouldn't do much physical damage. A cold Iron Wolf does much more, and can freeze monsters.

Defiance and might would boost both you and the merc himself. I guess both would be viable.

Also, note that, though I haven't played mêlée sorceress yet, plenty of other people I don't know have. I don't think there is any completely unused build, really :p .