Very much harder? I can breeze through Hell's Arena without thinking about it much on UV, and with a scout and hellrunner 2, I can clear the arena, grab the loot and go down the stairs before the nuke blows on UV AoRA without too much trouble. On N! I need a much more concrete strategy than 'corner shoot them all until they die', and I need to have more medkits for when corpse stacking doesn't go smoothly and I need to take a plasma ball to the face, despite the medkits healing double on N!. I also need more shotgun shells since I'll be killing and re-killing and re-re-killing. It's easier when the stairs to the arena appear on level 3 rather than level 2, and it's easier with shotgun scout builds where I have reloader 2 and +10% move speed, but I can do it fairly reliably now when the stairs appear on level 2 and I have a technician with son of a bitch 2 or something else that doesn't start shining until later in the game.
I use strategies like annoying demons and cacodemons with the shotgun at maximum range to draw them into a central location where I have a killing field, and when I leave my killing field to hunt for monsters, I keep an eye on the corpses; even when they're out of sight, the game still shows the corpses vanish when monsters resurrect, and when I see that happen, I know I have to go back and re-kill them before they wander too far off. I try to pick a reasonably defensible location for the killing field, usually near to the upper or lower outer wall in the middle region of the arena, but often I get chased off by demons/cacodemons coming in from two sides or corpses resurrecting on one side of me while I'm dealing with monsters on the other side of me and I have to start a new killing field elsewhere. When everything goes to plan, the corpses in the killing field will resurrect at a slow, manageable rate and I can gradually stack them on top of each other to dispose of them so that there's just a demon corpse or two left once the barons arrive, which I can sometimes stack on top of the barons as I kill them. On UV I can just run around and kill everything without worrying about any of the above.
The rocket launcher is an essential piece of kit when I'm doing the chained court on N!; sometimes I can knock the barons into the lava with my shotgun or kill them in a doorway, but usually I need the rocket launcher to dispose of at least some of their corpses. The rocket launcher also makes killing the arena master fairly doable; just hit him with a rocket every time he enters your field of vision and the knockback on him will give you time to reload and move a step or two, or even swap weapons and take out a former if you have juggler. If you miss and he raises his arms, put some space between the two of you and try to avoid the blast; the move speed bonus from the berserk packs help with that, and the 60% fire resist makes it less painful if you do get caught. I dispose of most of the formers in doorways before I face the arena master, so I don't get too many of them resurrecting while I'm fighting the arena master. It doesn't always go to plan if the arena master makes an early appearance or my berserk packs get destroyed by the barons, but such is life.