>>5366603A freshly spawned Spider Mastermind dies in 4 properly-aimed BFG shots. She got 2 bad shots on it, and a Baron was infighting with it as well, and THEN she got a point-blank shot off.
Doom 1 doesn't get particularly hard until E4, which was made after the game originally released. E1 is great, E2 has good maps and a good finale, but E3 is crap. E4 has a very brutal start and E5 was released 20 years later.