I do think the PA28 family isn't particularly sturdy but they aren't designed to be.
I know several mechanics that say the same about the TB, but I account it to their years of Piper/Cessna indoctrination.
They take a beating from students and survive, so they're not that badly designed. We've had two accidents where the main gear poked through the top skin though so there may be some dinky bits in the design...
I know for a fact that our ex TB10 had its moments but in general was pretty nice. Having said that, the flying Citroen is no match in sturdiness against my ex mount, the Commander 114B. Talk about over engineering!! I believe they had aircraft carrier operations in mind when it was developed.
Is that a GT you're flying IO540?