Daggers can roll up to lv8, but it's a really low % of damage increase compared to Amp (100%) when I look. Did they change the skill somehow? It shows 27% damage increase at level 8, which is the max level I can seem to roll as charges. It's worse than even Decrep, sadly, which is already worse than Amp.
I think the dmg increase with higher lvl charges is minimal.
This can't compete with amp or decrep on basis of dmg, but the difference is you can get these on accessory slots; while with the curses you have to equip on weap and deal with gold loss during those kills. Lethargy is also quite good as it slows down their attacks/frw by 50% (maybe less fleeing?) and defence reduction too. I'm spitballing here but there's definitely a use case on low gear lvl, and maybe even a use case at end game gear lvl.