You're speaking in generalities and most likely from a whole lot of bad experiences. I'm speaking in specifics and from two positive encounters. Think about it, though, in terms of weapon theory (which you tend to champion and are something of an expert in), why wouldn't an armory work, if all the weapons are away from their points of prime usage?
Well why dont I just camp right were all of the weapons are Hugh? Then all of those weapons are all in a prime usage, right? This is why you carefully place them across the map.
The player could run in grab the rocket, fire off all shots, possibly rack up a kill or two. Run back in grab the sniper... I think you could see what'd happen next. It'd create a massive choke point. Having power weapons too close together is just as bad; if not worse than having them in their prime vantage point. If you have an armory its best to use it in a minigame or very casual infection and limit the variety of weapons.
Ever see 300? Where the spartans lured thousands of the enemy into a tiny little crevice? They slaughtered them. Now, let's take it down to a smaller scale, and with a bit more related discussion. Halo. An individual goes into the armory, stays there, with all the weapons of it, you know, sniper/rocket/laser/shotty/mauler/etc..., and just laughs while fighting. Kind of like the Spartans did. =/ Just saying.
So in a way, armories are the birthplace of Spartans!!! "This is not fail, this is an ARMORYYYYYYYYYYYY" ... no its still fail.