After 50 the DEF effectiveness is halved, so 85-75=10%

IMO, Indom is more useful in tanking the Lindwurm. Leaving it to even 5% chance can sometimes be a disaster. A secondary swap tank and overwhelm suppress fire are always welcome too.

If you really hate the wurm that much and want to solo it, you can build a Anatomists potion charged bro to even kill it 1v1. It's not going to be cost-effective though.

Also, yes, a well built tank can easily survive 2 hits. 3 gets VERY dicey though. Sounds like you may have skimped on hp.

Don't use shield wall Vs lindwurms.
Indomitable indomitable indomitable

If you don't indom, you run the risk of being hit & stunned, which is terrible

When you run out of steam, use wait after your last indomitable. Ideally, the next turn your indom will expire after the lindwurms turn, you recover and then hopefully go before the Lindwurm again.

With indomitable you will be able to survive multiple attacks. A late game tank should be able to tank two Lindwurms and survive if you are not absolutely unlucky.

All defence above 50 gets halved, so that, with 100 melee defence, you're 50 above 50, meaning that the excess of 50 gets halved to 25, leaving you with actually 75 melee defence (although the character stats panel doesn't alter to reflect this, and the stat tooltip doesn't mention it). If you are an odd number above 50, e.g. 53 melee defence (3 above 50), the halved excess amount (3 halved to 1.5) gets rounded up, so that (in the example given) 53 becomes 52.

If relying on having actually minimal 5% hit-chances against you versus lindwurms can still be a disaster, Overwhelm is not a help, since it won't get those hit-chances to lower than 5%. On the other hand, Overwhelm can help to get higher (more realistic) hit-chances against you to the minimum of 5%, although this is much harder to do comprehensively against larger numbers of lindwurms, each of which has both a head and a tail making attacks.

In practice, using Shieldwall is often what gets a tank to minimum 5% hit-chances (or at least lower chances than before), and it is valuable for that reason. Using Indomitable is excellent security against unlucky hits, but it also means you'll max out on fatigue sooner and will need to use Recover - possibly with one or more wurms still to act. Wurms have decent initiative at the start of battle, but it (similar to that of unholds) quickly drops extremely low once they've been embroiled in battle for a few rounds, meaning that they'll eventually be slower even than a heavy tank who is exhausted, Dazed/Staggered, Brain-Damaged and has waited turn.

What I tend to do with tanks against lindwurms is use only Shieldwall in the early rounds, and wait turn after doing so, to increase the chance of being slower than the wurms in the next round and/or to recover from any unlucky hits that inflict Daze/Stun. If the tank gets hit and loses most/all armour, I might then use Indomitable as well (or even instead, if the hit-chances will still be low enough for any hit to be "unlucky").

At some point, I'll send non-tanks into direct melee engagement against the most damaged wurm(s), preferably to Daze with 2H maces or Cleave/Decapitate with 2H cleavers. Ideally, these non-tanks will be able to engage in such a way that they can only be attacked by the wurm that they're attacking, but this is unlikely in fights against larger numbers of wurms that cluster together (there's no perfect way of fighting these). Therefore, I may end up using Taunt with the tanks, to reduce the danger to the damage-dealers. Sometimes, I even end up using only Taunt (not Shieldwall or Indom) on the tanks - so long as the tanks aren't clinging to life themselves by that point.

Note that, because of the massive HP and armour damage inflicted by wurm hits, the unhold bone-plating attachment is extremely valuable against wurms. If Indom isn't available or active, Steel Brow guarantees that a tank with decent HPs can take one hit to the head without receiving an injury (although SB is often difficult to fit into builds, in spite of its situational usefulness). Nine Lives guarantees an additional hit without dying, but is also difficult to fit into builds.

A late-game tank should be able to tank 2 lindwurms, but late-game lindwurm parties typically contain 4-8 wurms (each of which has both a head and a tail).

Thank you for your explanation guys. Now I understand why lindworms can hit my tank bros.

I actually found the best way to deal with lindworms: lure them with a naked ranged bro who has pathfinder perk. When they are chasing the ranged bro, let your tank bro taunt one of them and all other bros take polearms (if a bro doesn't have polearm mastery, he can use goblin polearm, which cost only 5 AP). Each round with 9AP, a bro can walk close(2AP), poke(5AP), walk away(2AP). This way, you can kill lindworms one by one.

You have to admire the wisdom of human, killing the giant beasts with teamwork like always.

@overwatch_hope, yes, this should work well. However you don't have to use polearms to be successful. The wurm's body/tail doesn't have 2 range attack and share the hp pool. So you can stand 2 tile away from tail and >2 away from head, and keep hitting from there.

Bow actually does better hp damage once its armor is gone. If you can put one or two archer in an unobstructed spot, it can further speed up the killing process. But the positioning can be difficult, and I often find myself appreciating the range overwhelm to (flexibly) debuff the high ATT more than just raw damage.

In my silly gaming channel is a video of my peasants taking down 8 Lindwurms.

https://youtu.be/_mX_eu6R5Tg?si=pxymb0ZRL0gDjh_v

If you think Lindwurms are terrible, wait until you play Legends mod and fight Stollwurms.

https://youtu.be/-lyhRL-tZPE?si=mzPk8rzcq_Y6_p5T

I'm sure I make plenty of play mistakes, but maybe you also pick up some interesting stuff from these