At any rate: every member of Congress has a staff with a million dollar annual payroll.
Are they going to carefully review the TPP for problems? Of course not. But the negotiation process has nothing to do with that. They'll vote for or against free trade as a valence issue and nothing more. What few surprises we'll get will be a pure result of election year posturing against Obama.
As for whether this is a problem, again, I think that boils down to a valence issue. Either you believe that free trade and trade rule harmonization led by the US is a good thing, or you (reasonably) do not. If you don't, then the process we have now is terrible, because that process creates the potential that trade deals will happen. Because of course, if Congress was looped in on TPP negotiation from the outset, with advise-and-consent on each successive draft, there could be no trade deal. This Congress couldn't work out an agreement to fund a pothole repair if the repair was close to a contested district.
Remember here we're talking about Congress deciding about laws for other countries, much more so than for their own.