Yes, you might be right. Thanks for sharing your views, it's always good to question every view before making a descision.
Now, to air the views I've heard on the pro-external storage from others;
To run 12 simultanious guests you need either 1 high-end server in the range of 6k, 2 middleclass in the range of 2k or 3 low-end in the 1k range. I'd say that's about where my setup today lies, 2 low-end and 1 middleclass. Depending on how long I can count on the external storage, it might come down to a price issue. Every year I get from the external storage I save roughly 1k in saved investments. I'm not entirely convinced myself as it's kind of an unsure way of counting in my opinion, but still there might be a point there. One of the cons to this idea is that I don't even know how much juice I can squeeze out of a DL360...
Another pro-external storage arguement is simply redundancy. 3 hosts + 2 external storages (if counting in the NAS) = spread risks. Hard to argue. If it's set up correctly that is.
A reason I myself find interesting is the functions that come with the QNAP. Things like Rsync, cross platform support, iSCSI LUN snapshot feature and backup features for smartphones with an app that lets you reach pictures like a cloud service. All in all you get other features that can and will show useful, if using it for more than just external storage for vmware.
At the same time I wouldn't mind having a little more juice in the host, and for 6k you get quite a lot. And as you point out, 4 or 6 hr support, although I'm actually more of a hardware tech myself and usually fix all of those problems myself. Only trouble is when you can't get spare parts within a reasonable amount of time. Then you're screwed either way 