Look at it this way...if you don't have an EGT gauge you don't know about all those potential problems either. That's why you are going to put one on. The addition of a single EGT near the pistons is a solution to give average conditions. You can add another to the other head, or, realistically not expect a weird failure during normal operation. Sure, the other side of the engine could be gone to hell like you describe. Would you know it without the EGT at all, would you know it with the EGT post-turbo??? Maybe, maybe not. Probably not.
Like everyone is saying, it's your truck. The EGT is to let you know if you're pushing too hard...not necessarily if something has come unglued. Like DaveBen said, that's a nice approach for the airplane guys...and they measure "pre-turbo" for sure. All cylinders.