I remember having a bias against the flood citing their levels as boring. However I must confess, most of my reference points were from halo 3 and to an extent 2. I also gotta say this will be a long, hopefully thought provoking, post.
However after replaying H1 on Heroic (my personal favourite campaign from beginning to end) and spending time playing on Keyes, The Maw - I realised/remembered a few things:
I still don’t particular like the Library, but Cortana in H3 is SO much worse to me
The flood in Halo 1 really do overwhelm you, seems they attack in greater numbers. This makes the shotgun a God send against them.
The carrier forms seem to have bigger explosions, once again this may have been the effect of the skull I had equipped
You have to adapt your playstyle when dealing with them compared to covenant and sentinels. Flood would rush you, push you out of positions etc
I can’t confirm this, but combat forms seems much faster and more ferocious (this could’ve been as I had the angry skull on). The flood are also more durable in Halo 1 generally. Our melee is overpowered in h3.
A key part of the flood in the 2 levels I mentioned above are there are sections where the flood will CONTINUE to respawn unless you bypass certain points in the level. This is KEY and means that you can’t just pick them off from a distance and adds to the sense of urgency. Severely lacking in h3.
Because of the above there were times, especially in the level Keyes, where I’d use the covenant vs flood skirmishes as distractions to help me progress. The 2 times in particular were when the carrier forms infinite respawn from a lake, before you reach the taken over Truth and Reconciliation ship. Second time was after you find Keyes when he’s become one of them and you’re ambushed by flood, but covenant are waiting outside of the room.
Flood would sometimes come back from the dead!
No annoying forms that would keep you pinned in cover, like that form in h3 the one that can transform. When fighting the flood, you should be forced to stay agile, to further differentiate from covenant. Literally should be like fighting a zombie horde.
As 343 seems to be using H1 primarily as a source of inspiration, I hope this extends to the flood IF they are included in Infinite. And they build off these foundations and make the flood stand out and ensures the players respects their presence on the battlefield.
TL:DR
The flood ultimately were more of a threat in H1 and were more enjoyable and stood out more due to reasons such as constant respawning encouraging movement, being quicker and generally overwhelming us. Wouldn’t be wise to adopt the same tactics you would against covenant, giving them more purpose (lacking in h3 IMO). If they return in Infinite I hope 343 builds of their H1 iteration and their purpose in that game.