Most of the axle breakage I have seen are Dana 35 rear with Detroit Locker and a 4.0L which has more torque than a 4banger.
Yeah Mark, every broken D35 photo I've ever seen is usually showing a rig with 33" tires, probably locked in the rear only, 4 or 6 cylinder (but likely 6).
This all makes sense. Somebody buys a Jeep (likely 4.0) and they want a lift and big tires. So they get set up with that and take it off road. Traction still suffers so they ask around about a locking differential. Everybody says lock the rear first. So, they lock the rear. Then, they throw it in low range, take it off-road, end up unweighting the unlocked front so its just the rear that has traction. The rear end slips a little on dusty rocks before getting a grip and "snap."
I dunno about stopping D35 axle "tube" bending, but I speculate that chances of outright stock axle breakage in the D35 could be greatly reduced by making sure your Jeep's front end always has traction off road. Lock the front, if you lock the rear.
I run a locker in the front, not the rear. What sucks is, I could probably end up having an axle snap in the front if my rear end loses traction. I think you need to have front and rear lockers and that the D30 probably isn't any better than the D35 in terms of "snappage" vulnerability using a single locker - small tires and the 4 banger are probably the only thing keeping my front axles in tact so far