In my opinion, if you're flying DL in J to Asia you're doing it wrong unless the fare is much cheaper than on NH, JL, SQ, CX, CI, KE or BR. I rank Delta about the same as AA, UA, Vietnam and the mainland airlines in China.

I only take a US airline to Asia over airlines in that first group if they are much cheaper or have a non-stop and a connection doesn't make sense.

DL is relatively competitive to Europe and is definitely competitive to Latin America.

Of course, the above is based on my experiences and what I do. YMMV.