In my experience, extra rods (beyond the truss rod) are not necessary in a neck as long as the wood used is dry, well-seasoned and quater sawn; all glue joints in the neck are very good (both surfaces flat to .001" or .0254mm) including the fretboard-neck joint; and the frets are well-installed.
[i]Also make sure that the truss rod is very tight in its channel[/i], a truss rod that is loose or comes loose later can rattle or vibrate sympathetically with the strings, a possible cause of dead spots. The truss rod being tight in its channel is [i]very[/i] important. Knock on the neck with your knuckles throughout construction to make sure you don't hear the rod rattle. But, don't listen for rattle unless you have all the tuners and hardware off the neck, and if adjustment nuts or washers are on the rod when you do it, make sure to tighten them a little, all these things will rattle a little and you'll give yourself a heart attack when you mistake them for truss rod rattle after you've put 20 hours into the neck.
I've never had a dead spot on [i]any[/i] of the necks I've built this way.
However, there are lots of very good luthiers out there that swear by stiffness rods and I'm sure they make them work quite well.
Keep in mind that you don't want a stiff-as-concrete neck. You [i]need[/i] at least a little relief to be pulled into the neck by the string tension or you won't be able to get really good, low action.
Good luck on the build! Do we get to see some pics?