Agreed. The problems with selling trade agreements is that the benefits (while real) are diffuse while the drawbacks are felt more severely by a small part of the population. It's entirely rational for US manufacturers to be against trade deals, and indeed a lot of such people have a lot at stake. However the benefits of cheaper goods while shared by vastly more people (including those not yet entering the workforce) is harder to notice.
With some exceptions (biologics) you're right on copyright, and I'd agree. However this only tempers my support of what I consider to be an important geopolitical move.
I won't claim any kind of expertise on the non-tech-related effects of TPP; I'm not an expert in international trade.
With respect to copyright, patent, and trademarks, however: I really don't care about "investors" who want to make other countries follow more draconian regimes in those areas. There's a happy medium between "zero acknowledgement of foreign copyrights at all" and "ridiculously excessive copyright laws"; ditto for patents and trademarks. TPP just directly exported the US's ludicrously excessive copyright, patent, and trademark laws, complete with DMCA-like provisions and criminal (not just civil) penalties. Those terms at a minimum needed fixing, and I think the people arguing against TPP in its current form on those grounds alone were right to do so.