The companion you have probably level capped a few levels below you which is why they can't hold their own. Mjoll caps at level 45 for instance. I'm level 55 or something and the Markarth house carl holds his own rather well. If you like the guy you have though, just give him the final Dragon Mask which has a chance to heal and damage enemies. C:

Also, I read all about the Falmer and now I don't hate them quite as much. :C