That works for imaginary numbers, sure. It works for RTS games too. But, unfortunately, development doesn't works like Warcraft - you can't simply take a peon away from cutting wood, assign him to build something instead, wait a little and... ta-da it's done like magic. Developers have different sets of skills, different focus, different assignments. As I said to you already, there are at least two Developers working on stuff that isn't Lordaeron that I know of. Are they fixing what you call critical bugs? I don't know. I wouldn't be surprised if they couldn't on their own and needed other things fixed along by more Developers, who are working on Lordaeron.
So what will you say next, that then more should be assigned, in detriment of Wrath of the Lich King? Well, it's good that you bring up again the matter of time, something I dismissed before. Not because it would give you reason, more like the opposite. You're waiting for fixes for an year? Well, people who play Wrath of the Lich King have been waiting for the fixes they are getting now for like five.