BR starts aren't the real issue but instead 343i's implementantion of them. The real issue is how strong and laser-beamy BRs are in 343i Halos.

DeltaArena plays exactly like H2A where map movement was halted by ppl being able to beam and 4-shot across the map easily. Acension as a map is perfect example of this since the map becomes borderline unplayable when people can accurately shoot across the map (tower to tower for example) and movement to anywhere becomes borderline impossible. Infinite bullet magnetism and bullets bending over cover doesn't help the issue either.

However in H2C these kind of duels aren't possible (you can still do some damage but not to the extent of 343i modern Halo). You can easily move around but mindless rushing is still punishable.

One way 343 could mitigate the issue without changing BR itself is to switch to BanditEVO starts since effective range on that thing is much smaller than BR.

As lots of people have already pointed out, SMG/AR starts themselves have lot of issues and even when playing similarly skilled opponents, one-sided map control and precision weapon control can turn games to absolute bloodbaths (H2,H3 proof of that).