I think we're looking at different printings of Fire Shuriken. Spell Compendium, pg 92. It's an Instantaneous spell, so you can stack them up during downtime, meaning no actions required in or even shortly before combat. They do 3d6 fire damage each, so average damage from using platinum coins doesn't equal it til level 10.
Spell Resistance is not an issue, because the spell doesn't affect a creature (it creates an object), so there's nothing to resist. Honestly the SR: Yes entry doesn't even make sense.
The damage type bit comes out to be a wash, because Fire Shuriken ignores all damage reduction anyway (though is effected by energy resistance, as you said), and a Lesser Rod of Energy Substitution is a thing.
Really, the only thing that Coin Shot has going for it is the touch attacks, which I will readily admit is rather nice.