Our Enspell IIs are crap no matter how you slice it, but I prefer to forget they ever existed instead of hopelessly trying to fix them.
I would rather fix them. They are subpar, but not nearly as much as people are making them out to be. Just changing the +enhance to be at casting would be a great enhancement. As awesome as dual-wielding EII would be, I do believe that would be too much of a boost. I would rather have the second hand be a samba or some other enhancement.
Maybe create a Tier III that gives some sort of buff/debuff and only works on the off-hand?