Ignoring d20 modern, as it just follows a different concept than D&D, lets look at manyshot. This hack feat, first published in the epic handbook, allows you to string and fire 2 (or more) arrows and use one attack to fire them. That is multiple arrows, so the DR issue is clear. Also, the feat should require different attack rolls, so Robin Hood style double shot works out.RangerWickett said:2. There is a precedent for a single roll representing multiple attacks, with the multishot feat, or with autofire weapons in D20 Modern. In one of those instances, the two arrows have to penetrate DR separately. In the other, the three bullets count as one hit. I admit, my solution isn't factored into the rules as smoothly as I'd like, but the fix is simple. A single shot has multiple rolls for attack and damage, true, but when that arrow hits, the DR slows it down, so every one of the damage rolls is lessened. I don't know. It sounds fine to me.
D&D isn't nearly as abstract as other RPGs.