The choice of Rakks made by GBX almost feels trolly in nature XD. Bloated Rakks that never stop moving and keep dropping enemies that will not let you stand still, Badass Rakks that have AOEs that can cover about a 4th to a 3rd of the entire area based on there location and Shock rakks that are not as bad but love to divebomb you. Also I would mention that both Bloated and Badasses are pretty spongy.
Outside of homing grenades, and Atlas weapons they are really annoying to deal with and just make some waves drag unlike the other two circles of slaughter which keep a pretty good pace with the right set up. Outside of using Iron Bear on Moze with auto bear, or Rakk Attack on FL4K I never have a good time with this part of the Circle of Slaughter and honestly iv started to outright avoid it when starting new games.
I feel like arena also caused the Rakks to fiddle around in serpentine patterns more then they normally do in open areas on Pandora. Lastly iv had a couple occasions where they have just decided to fly though the left side of the map for a couple minutes making the waves take even longer.
I honestly with they would not have more then one badass or bloated Rakk active at a time making it far more manageable.