I'm going to disagree with your Halo CE accusations on the flood. Halo 2 flood were harder to kill. Thats that. Ho.
Posted by: Sliding Ghost
Which Flood are you talking about?
Flood in canon (Halo novels), feral Flood, proto-Gravemind Flood (or is there no difference from feral?), Flood led by a Gravemind, or Flood in gameplay?
The Flood in gameplay gradually got worse to the point (in Halo 3) that they (combat forms) only present a threat in numbers or if they have shotguns, maulers, heavy weapons, or the energy sword. The shielded Elite combat forms that have plasma rifles can also be a threat if you don't take them out quickly. The feral Flood in Halo 1 were much more scarier and dangerous.
Infection forms under Gravemind's leadership are relatively tame as well and hardly any challenge. The Halo 1 Flood were easy to pop with melee but they were only dangerous if your shields were down.
The Carrier Forms were lacking in charisma in Halo 3. I've found that they can jump in Halo 3, but this is near useless because it's so rare. Their AI should be made stealthier (e.g. Carriers ambush marines by leaping at them and exploding in their midst rather than foolishly charging at them, Carriers use active camouflage).
The Pure Forms were a nice addition, but it was disappointing that three out of six got cut.
Tank Forms are easily defeated by the Energy Sword. I've seen them run. Imagine one running at the Covies and then leaping into the air and landing in their midst. Or knocking down Covies. Also, not only should they be able to regurgitate infection forms, but they should also be able to call nearby pure forms for assistance. And I've sure we have all seen what happens when ranged forms work together...
Finally, the Juggernaut. I have nothing more to say. If Gravemind had hundreds of these at his disposal... these necromorphs wouldn't stand a chance.
No actually, there's one more. The non-canonical half-infected species (Elites, Brutes, Marines).
If they had been intended in gameplay, then they might have retained their shields (if they were Elites or Chieftains), making them very formidable since they have mixed AI. These could also act as infiltrators (on higher difficulties, the Flood spores on their back disappears entirely, making them appear normally). In real life, this would be terrifying.
Imagine you're a Grunt and the Elite leader is actually a half-infected Elite. The Flood AI allows the Elite AI to have control until it decides to take control and "suppresses" or destroys it. The half-infected process does not kill the host. Rather, the infection form knocks the host unconscious (by causing intense pain) and then infiltrates the host unnoticed.