Do you consider going WOT Abusive?
In my younger years, NO.
After working as a heavy diesel mechanic for many years my answer now would be, YES if done in excess.
After more inframe engine overhauls, trans, power divider, rear axle, transfer case rebuilds than I can even remember I can say with no doubt that yes, excessive WOT is deadly to any drivetrain. WOT places all your engine/drivetrain components under the highest stress levels they will ever encounter. It increases preasure and load on gears, engine components and anything else that moves. It increases operating temperatures that also stress components and raises the lubrication fluids temp's which shortens their life. In large diesel engines it is also the most likely time that cylinder liner cavitation will occur.
"WOT is needed to keep the engine free from carbon", since when? If a engine is running properly carbon or soot build up in a engine should not be a problem. Yes putting around town like grandma can cause deposits but a good steady cruise down the highway from time to time at reasonable speeds and throtle can take care of that. If you have excessive deposits you have something else causing the problem, not lack of lead foot application.
If WOT was good for a engines life span you would think race and high performance engines would last for hundreds of thousands if not millions of miles. They have had more blueprinting and balancing done to them than most people can even imagine yet they only last a very short time. Why? Because they are used at WOT.
So am I saying you should never go WOT, heck no, enjoy your vehicle and what it can do. Just remember that anything done in excess has a cost.