Oh, I'm sure I was on the shitty end of that one, too.
The word "once" is never mentioned in the ability description (RE: 13th-level Full). Yet you (et.al., previously) consistently ADD that word.
Again, the sword+spell doesn't care whether it's 3 targets once each or 1 target 3 times -- it literally can't tell the difference.
Such as:
- swing #1: target = goblin #123
- swing #2: target = goblin #123
- swing #3: target = goblin #123
That's 3 targets, in that with each swing, each swing individually and independently targeted a creature. The only thing that knows/care that all 3 of those targets were one-in-the-same is the target itself (and, well, me personally). Sure, spells that specifically call out "multiples don't stack" are their own thing, and are adjudicated accordingly. But otherwise, it doesn't matter.
The ability as interpreted by not-me is crippled, lame, and lazy; and not worth the ink that printed it. wiz/sorc + spellsword is leaps and bounds better than Duskblade-according-to-not-me; given the timeline of publication and the intentional evolution of class design in the intervening time, the not-me duskblade doesn't even fit into the paradigm.