Of course, on TATL, if you get upgraded on a domestic leg before your longhaul, the standard baggage allowance (2x50 for elites) still applies. I think there's even an FAA regulation somewhere that states that baggage allowance is dictated by the longest leg (I think it has been referenced to me by an agent once) but I haven't taken the time to verify that.

If Delta wanted to simplify their horrible baggage chart, they could easily put together a tiny web app where you would input your origin and destination and it would then spit out the baggage allowances by class of service, military status, elite status etc. Or you could even enter those parameters into the app along with the destination information, though the risk is that if you have too many variables, people will get confused.