>I actually would love to see
>rangers/thieves/mages/communers/etc. get legacies, or

This has happened a time or three, although seeing non-warriors with legacies always made Valg sad.

>warriors/thieves/assassins/etc. get a spell or two.

This probably has happened more often.

That being said, generally speaking, the way our infrastructure is set up, if an ability usually goes to all members of a class (e.g. demonfire, an ability all shamans have), it's prohibitively difficult to give it to a single member of a different class. So it's more unique spells and less cross-class abilities.