As some people have mentioned, the gap between Hard and Suicidal is too large and I would go as far as to say that it is at the point where you'll still want to play on Hard if you're at Level 24 or below. I think it would be worth it to opt for 5 difficulty levels rather than 4. Maybe this would work?
Beginner: A rebranding of Normal. recommended for Perk levels 0-9, depending on perk choice.
Normal: Rebranding of Hard. Recommended levels are 5-15. Starting point should be handled on a per perk basis (some perks can go as early as Level 5, other perks should wait until Level 10)
Hard: The old Suicidal difficulty (Before Update 1066). Should be playable for perk levels 15-24, 25 if soloing.
Suicidal: The current implementation. Level 25 and multiple players recommended.
Hell on Earth: The current implementation. You will not survive.
Beginner: A rebranding of Normal. recommended for Perk levels 0-9, depending on perk choice.
Normal: Rebranding of Hard. Recommended levels are 5-15. Starting point should be handled on a per perk basis (some perks can go as early as Level 5, other perks should wait until Level 10)
Hard: The old Suicidal difficulty (Before Update 1066). Should be playable for perk levels 15-24, 25 if soloing.
Suicidal: The current implementation. Level 25 and multiple players recommended.
Hell on Earth: The current implementation. You will not survive.