I'm just going to assume you're using Base Gil to make it fair.
Brahmastra is nothing compared to Ea. Brahmastra's rank is A+, and Ea is ranked EX. Even ignoring feats, this automatically puts Ea much, much higher than Brahmastra through background lore alone. Karna's version of Brahmastra, and the superior Brahmastra Kundala, are only rated Anti-Country at best. Ea is Anti-World, and has shown planetary feats to prove it.
Vishnu Bhuja is inferior to the Gate of Babylon. This has always been the case from the very beginning of Fate, that no matter what weapon or tool a hero possesses, the Gate of Babylon will have something with the same function but better, with few explicitly mentioned exceptions. Gilgamesh has everything humanity has ever invented throughout all of time, from something as ridiculous as interstellar travel to something as mundane as a hot spring or wine.
Heracles and Lancelot have never been comparable to Gilgamesh. In close combat, they - as well as Rama - far outclass Gilgamesh, but close combat alone has never worked against him. The one time Lancelot took on the Gate of Babylon, it was barely opened. In the original LN it was even stated that had Gilgamesh opened the Gate just a little further, Lancelot would've been overwhelmed.
When it comes to Heracles, even if he was busy protecting Illya instead of fighting all-out, he was still killed several times. Unlike Heracles, Rama doesn't have multiple lives. He doesn't stand a chance in hell.