Gen1 TORSEN was not the cause of IWE failures, that's a seperate weakness inherent in the IWE design.
To me there is no downside to having TORSEN up front. Esp if you crawl once and a while.
TORSEN is necessary if you want that front end diff to pull you up a steep climb, and helpful in other conditions as well. It's far superior to other LSDs in that it kicks in Without ANY loss of traction. Think of it like an automatic locker except that it multiplies torque right before you need it most.
It's an option because it adds to the raptors ability and without it your not getting the best raptor from a technical standpoint. Don't compromise, TORSEN is all that and is not any more failure prone than w/o TORSEN.
The association with CV failures has more to do with people messing with the front geometry by adding height (top perch) which compromises the CV and IWE under extreme conditions.