Those aren't the only use cases though. As I understood it, the issue is with the offhand weapon not doing anything, even if the range requirements are met:
1. Wand main hand, sword offhand, ranged: only wand shoots. Makes sense.
2. Sword main hand, wand offhand, ranged: can't shoot. Doesn't make sense.
3. Sword main hand, wand offhand, melee: attacks only with sword. Makes half sense.
4. Wand main hand, sword offhand, melee: attacks with wand, but not with sword. Doesn't make sense.
I haven't actually tested this myself yet, but sort of forwarded the problem from the Steam forum:Wand+Sword/Single One-Handed Disappointments
When equipping a wand and a sword, the player will only attack with the right hand item, range regardless, whilist still incuring the dual wield penalty.
As an aside, the author also laments that there's no advantage at all to using only a single one-handed weapon (as opposed to dual wielding, sword+shield or using a two-handed weapon).