I too had issue with the spider ambush on hard playing with two freshly created champions, an alchemist and a barbarian.
If you don't have a lot of herbs I would agree that you're probably in trouble!
It's a legitimate criticism of this mod however It's clear to me that when playing in hard mode it's intended for a stronger imported main game party. I try to anticipate the mindset of the mod creator when I'm playing these custom maps, They're not always nice and fair like the main game OGDA clearly likes throwing in the occasional toe to toe combat, So I try to save bombs and herbs for really tough sections that I assume will be ahead.
BTW if you think the spider ambush is too tough then you'll love the Ornate key area in the graveyard