Demolishers too easy to kill through some means.

[kittah_khan]

EDIT:
The bug I believe to be in play is that piercing projectiles and explosions appear to be registering multiple hits on a single demolisher by hitting multiple segments.

Nilaus aptly demonstrates the problem here:
https://youtu.be/QUfEEuM71C0?si=992UVv_mtesLIfQT&t=820

I also believe that this does not fit the design vision you laid out in FFF #429.
Based on the comments made in that article, I understand that the demolisher is intended to be a fight you undertake after preparing through stocking up on various consumables and laying a trap with various turrets and other deployables, preferably, lasting some time without being being a boring slugfest.

Unfortunately, I can't think of a good way to get the desired "bossfight" feeling within Factorio's current damage/health model, the interaction with stacking research, AoE/Piercing weapons, base resistances and regeneration means it's hard to achieve the desired result without it either being too hard or too easy, depending on the means employed and how far along you are in research/ammo quality and what resistance, health and regen values you assign to the demolisher.

The best suggestion I can think of is a combination of three things:
1. Reduce damage instances based on how much they overflow a fraction of max health.

As an example, if a damage instance were 50% of max health, the fraction 10% and the reduction 75%, a 50% max hp damage instance would resolve as 10% + (40% * 0.25) = 20%

2. Introduce a reactive resistance to encourage damage type diversity, this would involve demolishers gaining resistances as they take damage from a damage type, this reactive resistance would fade over time, like some of the slow stickers can do.

As an example, if you were to shoot a demolisher with a railgun, the demolisher would progressively gain kinetic damage resistance with each damage instance it suffers from the railgun, based on what fraction of max hp that instance did, that reactive resistance would then fade out over time.

3. Reduce a projectile's damage by a fraction of how much damage it has done to entities it has pierced through, modulated by the projectile's max piercing value, or prevent projectiles from interacting with the same parent entity multiple times outright.

1. Would prevent demolishers from getting one-shot by a single damage instance.
2. Would prevent demolishers from getting cheesed by a single damage types and/or nukes.
3. Would prevent piercing shots from doing massive amounts of damage with weapons that pierce multiple segments.

this should keep demolishers killable through planned means while reducing the impact of anti-climactic options, like, say, nukes, railguns or massed uranium mg turrets. You could even relax some of the resistances the Demolisher currently has.

[Rseding91]

This is a suggestion. Suggestions do not go in bug reports.

[Vulkandrache]

Nilaus aptly demonstrates the problem here:
https://youtu.be/QUfEEuM71C0?si=992UVv_mtesLIfQT&t=820

What problem is he demonstrating?
He has a bunch of damage upgrades.
The whole point of worm types is that they have multiple segments that can all be damaged.

this should keep demolishers killable through planned means while reducing the impact of anti-climactic options, like, say, nukes, railguns or massed uranium mg turrets. You could even relax some of the resistances the Demolisher currently has.

There is nothing anticlimatic about removing an obstacle thats in the way.

[kittah_khan]

To quote FFF # 429
"Demolisher combat can be fun and strategic. Each one is a boss fight to unlock a new territory. Demolishers are definitely the toughest enemies in the game. When something which at first seemed impossible to kill, can later be killed quickly and efficiently due to a well-executed plan, it is very satisfying."

The design intent of Demolishers is to be a bossfight, something that takes a bit of prepwork and lasts for more than a single second.
"I rock up and euthanize it" is not much of a plan....or a fight, my suggestions are specifically there to enhance demolisher survivability against (accidentally?) hyper-effective weapons.

What problem is he demonstrating?
He has a bunch of damage upgrades.
The whole point of worm types is that they have multiple segments that can all be damaged.

Examine the base damage of the railguns (10K) compared to demolisher health (30K small / 100K medium / 300K large, all with roughly 8% hp regen/sec and 50% kinetic damage resistance)

Going by the numbers, small demolishers are intended to survive several simultaneous unupgraded railgun shots (5K health lost per shot, after resistance), but the fact that each segment a railgun shot travels through counts as a new hit will very quickly result in even a single railgun shot outright deleting a worm.

But to return to the example, where a SINGLE personal railgun shot outright deletes a small demolisher? If you were paying attention, he mouses over his railgun ammo after the fact, his research adds a "paltry" 120% damage, so a single shot SHOULD be taking off 11K health.

The same "I can hit multiple segments with one shot to amplify my damage" problem applies to all piercing/chaining/AoE weapons, but for most weapons, it's not really a problem because the number of segments that can be hit is limited, or the base damage is limited.

[ChrisMcD2]

I agree with kittah_khan that it feels like a strange power spike when unlocking the Railgun. For me, Demolishers previously needed a strategy, a number of static defenses, and a risky lure of the Demolisher into that trap. My setup could only take on small Demolishers, and would always lose like a dozen gun turrets. After the personal Railgun is unlocked, for the cost of a single ammunition I was surprised to discover I could one-shot a large Demolisher from behind with 0 risk. It makes sense to be a large power spike because of the multi-planet unlocks required, but I also did similar math and expected a fight with large Demolishers and the shooting speed of 0.5 projectiles per second to be a challenge (not realizing that it would apply the damage 20x because it did 10k damage to each segment when lined up).