I don't like using flavor text as a guideline for rules; I think whatever fluff text appears reflects simply how a power might look in combat because combat is what the writers had in mind when they wrote it. I don't think fluff text is supposed to reflect any solid definition of how a power works or its limitations. That being the case, I have let swordmages use attack powers out of combat to take advantage of their utility potential, and I'll allow it again if it ever comes up.
Further, and I don't mean to sound judgmental when I say this, but I'd be annoyed with a DM who ruled otherwise. Because, while it is worthy of OotS,
is patently absurd and has no place in any game, unless it's a diliberately tongue-in-cheek campaign. If a DM ruled against using an attack power's utility potential outside of combat, I'd start to think that he was looking for excuses to screw the PCs over. I mean, what's more reasonable: that Dual Lightning Strike reflects a character's expertise in combining two distinct abilities [that he had to learn separately first and are independent from one another], or that Dual Lightning Strike reflects a bizarre spell that requires the character to attack [and that the spell somehow knows the difference between attacking the air, which has no hp and attacking an air elemental which does]? I'd say the first one is much more likely.