If you have completed Hell's Arena, you will already have a rocket launcher, which you can use to shoot down the necessary walls and then kill the last monsters from a distance, without crossing the lava. This is how I usually play the level. You will probably not be able to get the ammo back there if you do it this way, but then again, at that stage in the game shells are plentiful anyway, and you won't have any use for power cells for a long time.
I like the change, on Hard difficulty, from all former sergeants to mixed former sergeants and former humans. The best change in Chained Court in 0.9.8.10, though, is definitely what the Large Health Globe was replaced with--that health globe was fairly useless before, because of all the berserk packs on the level, and what it's replaced with is far more useful.