If dealers are the ones held responsible for TPA mistakes, that will help plummet the market for graded cards.
Personally, I think dealers should take much responsibility for what the sell (even with the have LOA's etc), but also know it's unfair for them to take full responsibility and physical examination of items they can't physically examine because of they have been entombed in plastic since they had it . . . But, if they are held fully responsible, that is why the market for graded will plummet. The dealers won't have confidence in the grades/authentication, and, when buying and selling, will be wary of the TPA's opinions. The TPA opinions won't mean as much to them, and, if they are fully responsible despite what the TPA says, the dealers may no longer wish to get the items graded.
It also may result in TPA's being used and considered for what they really are: giving a second opinion-- nothing less, but nothiing more. They will no longer be metaphysical arbiter and financial guaranteer.
Duly note that TPA's being treated as arbiter of truth is largely a matter of the buyers and sellers, not the TPA. For example, the TPA autograph LOAs specifically say on the letters that they are offering opinions (it's literally there in black and white). It is the collectors and dealers (rather, many of them) that treat the letters as something more. The TPAs don't sell the cards or autographs-- it is the buyers and sellers who, on their own, construct that market and its axioms.
I rail against the registry and its dubious statistical calculations. However, in defense of PSA, they don't buy or sell any of the registry sets or say how they should bought or sold or priced. How the sets are bought and sold, valuated and considered vis a vis the registry rankings is a construct of the buyers and sellers.
To put it into Seinfeldese, with all the drama and moral angst about who deserves credit for handing Elain the big salad, the punchline was "It was just a big salad."
The big salad
So, yes, the PSA registry is just a big salad-- which some might say implies that the buyers and sellers are a bunch of George Costanzas (with a Newman or two thrown in).
And, no, no one is saying there's anything wrong with a big salad. I like salad. Just don't base your religion on it.