>With this equipment I beleive I should be getting backfist
>attacks* but I don't beleive that I do. If the check is still
>there, but I've just been unlucky, please excuse me for being
>stupid.
>
>(*) An assassin with this skill is able to take advantage of
>openings in their foe's defenses more readily, gaining
>additional strikes in combat as long as they have at least one
>hand free of encumberances.<-- leads me to beleive this
>qualifies.

By design. If you are dual wielding anything, you won't get a backfist attack.