There was much more that could have been done in that regard with both Rose and Martha.

YES, there was! I suppose I might be having premature squee - I've been reminded that yes, Martha did too... but not as a regular thing, and for all I know, this is Donna's one chance to strut her non-Doctor stuff.

But y'know? Every person on the TARDIS brings their own skills, and maybe it's time that the show picked up on that more than once or twice per companion's run.