Wands do not constitute an itemization gap, since they are both equippable and are commonly equipped as a primary weapon by 9 of the game's 33 specs. You're describing a gameplay niche, or a type of mechanic that is currently unused or underutilized. This particular niche used to be filled as well, by all three cloth classes, but stopped being so when mana mechanics changed to make it much more difficult to run out of mana and have nothing left to use but a wand. Now it's conceivable that Blizzard could introduce a class that brings the wand autoattack back as a major damage source, but this would not be filling an itemization gap. Indeed it would have its own inherent itemization problems, because like rogues the class would be reliant on the drop rate of one type of item, with no real fallbacks.
This is not an issue which a class that could use, say, guns and crossbows would share.
I do agree that it's probably not the major concern or the starting point of any discussion regarding which class is next when they do their brainstorming sessions, but I also think it is something that they think about. Balancing gear drop rates is historically a recurring concern which they have talked about numerous times, and they know that nobody likes it when the second gun drops and the group's only hunter doesn't want it. Much less the tenth.
They would tie the character creation screen together, would they not?