The Sefer Hachinuch is explicit that Lo Sasur applies even nowadays (without a sanhedrin). So perhaps yes, one could claim that it applies to the gadol hador telling you something(The Rambam seems to argue, in hilchos melachim, , the Chinuch is definitely explicit, though)...
There is a very intelligent summary of the different positions in HaTakanos b'Yisroel Prof Yisroel Stefansky published by Mosad Rav Kook.
He states that there are 4 major positions regarding lo sassur as a doreissa prohibition
1) Limited to Beis Din HaGadol when they were in their proper chambers in the Temple - Rambam according to Margenisa Tova, Yereim. Ramban for things learned from the 13 midos,explanations of the Torah and Halacha L'Moshe.
2) Limited to Beis Din HaGadol but applies even when not in proper chambers - Rambam according to Lev Someach, Maharetz Chajes, Ran, Rashba, Rabbeinu Yonah, Ralbach. This is also relevant to the dispute between Rambam and Ramban in Sefer HaMitzvos #153. Ramban asserts Sanhedrin ended with cessation of capital punishment and destruction of Temple. Rambam asserts that every beis din hagadol has the status of Sanhedrin. Thus Rambam holds that Sanhedrin existed until Abaye and Rava - the fourth generation of Amoraim.
3) Applied to the end of the Talmud in the days of Ravina and Rav Ashi - Rambam's view according to Ramban and Chinuch, Rashbatz, Mabit, Lechem Mishna etc.
4) Applies in all generations even today concerning to the chochmim of the generation - Chinuch as understood by Minchas Chinuch. Rav Perlow holds that the Chinuch is a daas yachid
Lo sassur as rabbinic or asmachta
1) Ramban concerning halacha stated in the gemora. - Ramban in Sefer HaMitzvos. Ramban holds that rabbinic laws which are not founded on Torah laws - are not obligated by lo sassur even on the level of asmachta - even if these takanos were from the Sanhedrin. 2) Ran holds that as asmachta applies in all generations and even to takanos made by contemporary poskim.
He also notes that there a number of sources in the gemora which state that there is Torah obligation to listen to divrei chachomim and rishonim (Rosh Horius 2 2/Rashba Rosh HaShanna 16a) assert this is because of lo sassur