Thanks, but that assumes I already have max armour/physical/spell resistance, which I don't. I'm a Breton so my spell resistance is naturally higher than my physical resistance. So my spell resistance is capped, but not my physical resistance. I'm also wearing a light belt for the extra 2% health/magicka/stamina from Undaunted Mettle skill. So the difference between the two is 4323 (3960 from Breton Spell Resistance skill +363 from 1 piece Light Armour Spell Warding skill)

Currently I'm using: 81 Ironclad, 44 Thick Skinned, 49 Elemental Defender, 49 Hardy, 27 Heavy Armour Focus.

I'm trying a Magicka Sorcerer as a tank using a lightning staff. I use Inner Rage to hold threat on powerful NPCs and mass AoE to keep adds interested in me rather than everyone else. I'm aware this isn't a standard way of tanking but ESO's flexibility allows for crazy stuff. So far I'm doing OK in veteran dungeons but I'm wanting to try trials next and want to optimise as much as possible to give it a fighting chance.

OK I took your CP distribution, assumed max physical and spell resistance and reverse engineered it to get what mix of damage types would result in that being optimal. It seems that my guess is exactly what your distribution was based on: 35% direct, 15% DoT for both physical and spell. This gives me some confidence, but given the round numbers I suspect it was also based on an estimate rather than hard data.

In my experience it is best to keep it pretty balanced across damage types/sources as a tank because the role, to oversimplify it, is soaking up as much damage as you can so the rest of the group doesn’t have to. And the types/sources can vary significantly between instances, such as the Warrior dealing high physical damage while Z’Maja is exclusively spells afaik. Or the Earthgore Amalgam being exclusively direct damage I believe, whereas Thurvokun seems mainly dangerous because of its DoT.

If you do go for an imbalance, it is probably better to stack more into direct than dots, if anything; dots can be a death sentence but can also be healed over time. If you die from a big direct attack, not even a big burst heal would save you.

You can also consider what your healing sources are. This is kind of moot if you play with a healer, but if you’re relying on self-healing, classes with big burst heals likely fare better against direct damage and classes with strong hots likely fare better against dots. For example, neither my sorc nor Templar tank builds have very strong, instant burst heals, so I’d load more into direct damage mitigation. Even if they’re enduring a lot of dots, they have decent hots that are able to naturally keep up with those, whereas if they took a few back to back big direct damage attacks, their hots likely wouldn’t be able to catch up in time. So I want to mitigate direct damage further. By contrast, my dk tank build doesn’t use hots but has a big burst heal, so he can take a big direct hit and recover instantly from it even if another is incoming right away. But he’d have more trouble keeping up with dots if they become threatening because they’re constant and using burst heals that frequently would be too cost intensive. So for that type of build, I’d want to mitigate dots further.

Hope this gives some insight!