What are you talking about? Charisma is not useless at all, it raises your overall DT.
As a sniper class, It's normal to assume he will be out of combat alot more often then DT is needed. However, if he is going sniper, I assume this means hes going sneak, otherwise a sniper class is just going to be a gunner class which would be using high str and high endurance.
So a higher agility for sneak, for damage, high strength for carrying and melee since a sniper in close quarters is going to svck, and guns in close quarters, imho, svck in NV.
Since his Charisma isn't going above 5, dropping it a couple points isn't going to kill the game.
Since all the traits blow, you can download trait mods, which add 15 traits, one of which adds an overall DT.