I found the LST platform to be pretty fragile compared to my savage. The revo was as well.
The only "strength/durability" upgrades I've done on my savage-X so far is an RPM center skid to protect the brakes and rubber grommets behind the bumpers to avoid the bumper stand offs getting broke.
I have upgraded the diffs to XL, but that was more of a "worn out" issue than weakness/failure issue.
On my aftershock, I upgraded the arms, turnbuckles, chassis deck, center skid (almost required to avoid bending the trans input shaft, as I did), bumper grommets as well, new era roll bar, 4mm bolts for the shocks, alloy cases for the shocks, rc raven multi-rate springs, rpm arms, engine brace and diff collars.
Even with all that, I kept busting chassis rails. I busted 4 or 5 sets before I finally made a skid plate to tie the front skid to the center skid.
After all that, it was a tank that would rival my savage at the time. But each one of those upgrades was necessary for me to get it to be "tough".