Arena's are generally fun and challenging. I enjoy doing them quite often, but one thing that makes them difficult in a non-fun way is the lack of an option to heal before you start your first battle. When they're the first depth they're fine. You're at full health. Anything beyond that and you are suddenly at a huge disadvantage sometimes. Traversing into an arena with 1 health bar full is, well, pointless. Unless you're one of those players who never manages to get hit (a small minority of the population), you will die in the first wave.

And before someone mentions "what about the other floors that don't have those healing pads", well to that my response is thus: The mobs come at you at in far fewer numbers, making them far easier to deal with.

My suggestion will help keep the challenge of the arena's there while making it overall more fun. Besides, if it's not fun, why would I play it?