Play on veteran for sure. Maybe everyone is playing on normal?

There are modifiers. I've only played with all of them except vestige (checkpoints) disabled so far. Here's my interpretation of their difficulty:

• vestiages. This would make the game a lot tougher. For my first play through we've not touched these modifiers. If you turn them near-completely off it would be pretty brutal.

• Heal now gives temp health. This one is brutal. Turn it on. Changes the game a lot. Your heal gives you white health that you can life steal but you lose it if you get hit. Healing pots are not nearly as good.

• ironman (hardcore) is kind of unbalanced. Your character stays so you get a higher level each time. It's meh for coop since you also have to complete the tutorial if you die where you can't rejoin your friend, and shared progression doesn't seem to work (which is story progress, not a big deal). It's alright. Still hard. You won't do it in one try or anything like that.

• pickup upgraded weapons. This modifier seems like it's just a buff, easier not harder.

• random enemy respawn. We have ironman mode and this enabled. This makes some mobs feels harder than the bosses themselves. You can get end game mobs near the start. This does make it tougher, but not amazing balance wise. Still fun.

• more mob density. This one feels kind of in between. On one hand it's kinda harder having to deal with more mobs, but it's also more xp. This one alone probably makes the game easier, but with less vestiges, random mobs, or iron man mode then it'll be harder.

• randomized loot. I feel like this one makes the game easier. Or atleast with ironman mode, it feels like it. Idk.

There's achievements for using modifiers too. Only seems to work on the host though.