I'd be... cautious with adding abilities (like the broadsword example.) For instance, someone who's trying to keep a Natural character would probably be *irked* to suddenly be teleporting around (or teleporting people.)
As far as debuffs - and I just took a peek at my dark/dark's Confront - it does already do a -75% range for 12 seconds, which should help draw even ranged enemies to you. I don't know that scrappers need a damage *buff,* but a small set-thematic debuff wouldn't hurt. I wouldn't really even argue about a bit of damage (it would help the taunt function,) though the issue there is "do brutes and tanks get that as well?" (Especially tanks?) (Extra mention here for Dwarf form taunts, as well.)
There's already an IO that does a little damage (chance of, at least,) and I don't think anyone calls that gamebreaking, either, so I think that would be safe, in any case.