I see the Brothers as being resource-neutral, since you get a pile of gold and xp for relatively little effort
This is the case if you find them early and can explore to heal after the battle. Find them towards the end of exploration (which is very common if you do not have ENDISWAL) and they consume resources pretty heavily.
I'm certainly not saying the level is super-hard, but honestly I can't see putting it below Hexx Ruins.
I find Hexx quite irritating as I haven't figured out the trick to managing the revenants yet.
The trick is to focus on fighting monsters that are very high level. This causes you to earn lots of bonus XP and level up quickly. Although the revenants created will be quite strong, it's easier to avoid confrontation with a few strong revenants than it is to plough through a horde of medium-strength ones. If you have the IMAWAL glyph, it gets even easier: brick 'em. The venom ward item will let you glide through the dungeon with ease, as immunity to poison lets you casually defeat each revenant as you create them.
Paladins work too, but require proficiency with the religion system to get the most out of them.
Most people won't have Paladin unlocked until much later in the game, due to the vastly increased cost of the T3 guilds. If you have unlocked the Paladin, then his signature glyph (HALPMEH) can be used to cure poison and turns the level into a joke.