Not really. The flood's weakness changed in each game. In Halo three, the flood no longer died from melees and weren't as weak to the shotgun. The new shotgun was the sword, IMO. The sword just owns the flood. Its a one hit kill to all of them most of the time.
True, but you still knew the general weapons to use against them. Rapid fire weapons like the Assault Rifle, and the SMG, and close range Shotgun, and Sword. Sure they changed a little bit in every game, but you still knew their general weakness. Though, you can now get them with just about every weapon now in Halo 3, because you can headshot them, and you can still aim at the "feedlers".
I really would've liked Bungie too kept them true to Halo:CE's Flood by having them just rush at you in full force, in waves. Have infection, then combat, then the Pure forms all lined up and ready to go. Sure, it would've been tedious to fight, but isn't that what all Zombies are supposed to be like? Tedious, flesh hungry (or in the Flood's case, nervous system), drones.