Give them some staves. Lydia conjures up Frost Atronach, Familiars and she uses shock on the enemies and any other staff you can give her, including the Reanimate staff I gave her.
Also, I gave my Lydia a soul trap bow, some arrows and some soul gems and she helps to get enough to keep recharging our enchanted weapons.

Lydia's bandit...that she used the Reanimate staff on:
http://i1181.photobucket.com/albums/x438/Kicenna/Skyrim/TESV2011-11-1621-25-36-96c.jpg
:tes: