Well, it probably doesn't matter much either way.
Some would say the only real Tier1 companies are those that have the TDP (Colt and FN). Say what you like about the TDP specs, but they are they only measure/standard/what have you in existence.
I would say that Stag is capable of producing Tier1 guns, but choose to make stuff a little less so, perhaps based on costs.
LMT are generally considered Tier1 despite the strait pins, not parkerizing under the FSB, and the MIM gas key, but along with DD, Knights, Colt and FN, are the only serious military suppliers. BCM, Noveske (who to all intents and purposes, exceed the TDP), and now Centurion, are really the only other ones that I would consider Tier1.
I don't really consider fit and finish to be necessarily an indicator of quality. This is especially evident when you hear someone say that they compared their Norc/DPMS/whatever to a Colt, and there was less play between upper and lower, and the fit and finish was better than the Colt, and that this made their rifle "just as good as" or even better. It's more what the components are made of, and to what tolerances they are held. There is a well known maker of "just as good as" guns that uses parts rejected by Colt.
As for MPI, HPT, we probably agree, but I don't think it would really make much difference one way or the other with a well made component (eg: Filthy 14, HPT'd and MPI'd bolt and barrel, and still running way past what most guns will ever do, as well as thousands of military M16s, etc.). It's just that some of those who choose not to do it, and use that arguement, are known for making sub-standard parts and cutting corners, and the argument plays into their favour.
Regards.
Mark