Currently the only worthwhile protection enchantment is regular protection. It stops damage from all sources and does it just as well as the other types of enchantments. Sharpness is a similar problem. Instead of simply boosting weak enchantments, what if they were changed to become unique?
Projectile Protection
Ever been shot off a ledge by a skeleton? Projectile protection could prevent knockback from all projectiles, including splash potions and blaze fireballs. Ghast fireballs don't do direct projectile damage.
Blast Protection
If you are within an explosion's radius, the strength of the explosion is reduced slightly. This means that it will break fewer blocks and do less damage. If you are near the edge, the radius could end up being shortened so you take no damage.
Fire Protection
Fire protection should prevent fire damage completely like a fire resistance potion, but do damage to your armor. Essentially you would have fire resistance but useable whenever instead of being on a timer. Higher levels do less damage to your armor.
Bane of Arthropods
This is currently the most useless enchantment in the game. There are three enemies in the game that it works against, and two of them are rare and have low health. This enchantment causes mobs it affects to run around randomly for a few seconds instead of attacking similar to what animals do when you hit them.
Smite
Smite should cause a 2 second regen effect on undead mobs only. This effect does 2 hearts of damage.
Fire Aspect
Instead of increasing duration, fire aspect 2 does 1 heart of fire damage per tick. Each level ads another half of a heart to the damage.
New Enchantments
Frostbite
This would be a bow enchantment that can be level 1-3. It applies the slowness effect for 5 seconds per level. Cannot combine with flame.
Lucky Strike
This is a sword enchantment as rare as silk touch It applies a random potion effect with a duration between 15 and 30 seconds from this list:
Speed
Fire resistance
Strength
Instant Health (no duration)
Instant Health 2 (no duration)
Regeneration
Regeneration 2
Jump boost
Slowness
Slowness 2
Instant damage (no duration)
Instant damage 2 (no duration)
Poison
Poison 2
Weakness
Weakness 2
Wither
Horrible suggestions, in my opinion. I see nothing wrong with the current enchantments, and your ideas have been suggested before and will likely be suggested again. And if you think blast resistant armour being able to negate terrain damage is even feasible, you should attempt it yourself.
These enchantments are not useless, but protection or sharpness are always valued more. The reason people don't get upset over knockback or fire aspect is because they do something sharpness doesn't. If all enchantments did something unique, that wouldn,t e a problem. As for the blast resistant armor, the code already checks if the player is within range. The only change would be checking for blast resistance armor as well. The explosion power is a variable, so it would be easy to modify. At worst, the check code would have to be moved to before the terrain damage code.
Projectile Protection
Ever been shot off a ledge by a skeleton? Projectile protection could prevent knockback from all projectiles, including splash potions and blaze fireballs. Ghast fireballs don't do direct projectile damage.
Blast Protection
If you are within an explosion's radius, the strength of the explosion is reduced slightly. This means that it will break fewer blocks and do less damage. If you are near the edge, the radius could end up being shortened so you take no damage.
Fire Protection
Fire protection should prevent fire damage completely like a fire resistance potion, but do damage to your armor. Essentially you would have fire resistance but useable whenever instead of being on a timer. Higher levels do less damage to your armor.
Bane of Arthropods
This is currently the most useless enchantment in the game. There are three enemies in the game that it works against, and two of them are rare and have low health. This enchantment causes mobs it affects to run around randomly for a few seconds instead of attacking similar to what animals do when you hit them.
Smite
Smite should cause a 2 second regen effect on undead mobs only. This effect does 2 hearts of damage.
Fire Aspect
Instead of increasing duration, fire aspect 2 does 1 heart of fire damage per tick. Each level ads another half of a heart to the damage.
New Enchantments
Frostbite
This would be a bow enchantment that can be level 1-3. It applies the slowness effect for 5 seconds per level. Cannot combine with flame.
Lucky Strike
This is a sword enchantment as rare as silk touch It applies a random potion effect with a duration between 15 and 30 seconds from this list:
Speed
Fire resistance
Strength
Instant Health (no duration)
Instant Health 2 (no duration)
Regeneration
Regeneration 2
Jump boost
Slowness
Slowness 2
Instant damage (no duration)
Instant damage 2 (no duration)
Poison
Poison 2
Weakness
Weakness 2
Wither