IMO, the toughest carbon shaft I ever used is the now sadly discontinued Carbon Express Terminator Hunter. Fortunately, I have quite a stash and will be shooting them for years to come. This is my arrow of choice for all my Trad shooting & hunting.
They were not only tough, but were reasonably priced. With a little internet shopping you can still find them, I recently scored another 2 dozen for $112.50!
I believe you can still get Terminator Hunter Selects which are pricy but still less than many other CX offerings.
BTW, a CX arrow with the "Hunter" designator indicates it has the Buff Tuff wrap, normally the full length of the shaft. This wrap is the secret to their durability and also adds weight. Their arrows with the "FOC Technology" designator have the Buff Tuff wrap on the front 2/3 or so of the shaft.
I've always suspected the CX Heritage shafts are Terminator Hunters with the Buff Tuff wrap finished to resemble wood, rather than finished in a camo pattern...
Were I looking at a current CX shaft, I would go with the Rebel Hunter. Great GPI weight, Buff Tuff wrap, and much less expensive than the Heritage or Maximas...