I still think that a double steel would be incredibly useful, not necessarily at hand to hand combat as you would probably break bones and tendons as you mentioned, but you could still take peoples metalminds of the, before they are aware of you, if you compounded enough steel it would basically be a bendalloy bubble that only affects you and has none of that deflection going on, you could still zip around the battlefield shooting people at point blank.
But yes one of my second choices of twinborn is a Pewter/Steel although I alternate between that and a bendalloy/pewter they would do similar things but I think that for pure combat a thug-steelrunner would be one of the most useful.