will they be surivivable? Yes, definately
is it good??? heh... The problem being is that wraithguard have no hitting power, and how you kill this unit is you assault it. Baron himself is a joke in combat, and Eldrad only has 2 attacks... so all the CC falls on your Archon, who while is decent, isnt a hard nut to crack.
But give it a try and see what you think. Personally if I was you, and you are going all out to begin with, you might as well throw in a warlock w/ Conceal, so your wraithguard will have a 4+ coversave in the open (5+ from conceal, +1 from baron's stealth)