Weaker front diff? Compared to what? I have driven this thing all over North and Central America, including some of the worst roads out there. Never seriously rock crawled the truck but I have done a fair amount of off roading in Utah and Arizona with it. Never had any issues in 272k miles.
How does it compare with the locked ARBs I have in my Disco 2? Just curious as I've never had any issues with those either.
The two pinion front diff doesn't provide a whole lot of stiffness and allows the pinion gear to flex or break. The 4 pinion diff from 2000 on is less prone to this, but it still happens every so often. I don't know anything about your disco diffs, but the ARB carrier for the LC 100 completely eliminates the issue...
Don't get me wrong, the diff is fine under normal use, but is definitely the weak link in that drivetrain.