The plates don't conduct much heat but i'm betting the joints would let heat though a lot easier.

Underneath that is a quite thick layer of material that the marines wear, also the black carapase.

You want to go by lore? A smallest of breaches of the power armor will make for a sure and unescaepable death for the marine affected. Nurgle is the lord of decay and decay governs over both flesh and metal (see the Nurgle affected vehicles and armor, if a Land Raider can be turned into a bile pit on treads what hope does a mere marine stand).

And this is psychic power we are talking about, yet even a Plague Knife which isnt even a power weapon can breach power armor easy and spell death for the enemy.
Do you think the Imperiums doctrine for fighting the Plague Marines is to engage from range with the biggest ordinance (lascannons and missle launchers for example) for shits and giggles? Nope, they are a toxic threat that will breach your armor and kill you outright.

So no, its not lore abiding to have a plague last 5 measly seconds.

-what?-
Okay, I'm going to try to read between the lines here and argue based off of that, because I THINK I see where you're coming from.

Being environmentally sealed DOES normally block off airborne toxins/diseases. But Nurgle's diseases are warp-fueled travesties of existence and don't care about your filters. They still get through to absolutely devastate SM's of all types, trust me.
Ceramite is ablative but with a spray of promethium you're at least damaging the armor somewhat, which I would count as a form of damage to the SM.

Don't forget his pension for rusting metals. Anyone know if the tabletop game has any special rules for flamers vs power armor?

Thats what i meant when i said "decay governs over metal" above.

I think the LRs have allot beter anti-breach protocols than standard power armor.

I know its a model but that creeps me out, no way i would touch it without gloves.

Jesus christ that's an amazing conversion.

Again, I believe in terms of game play, each DoT in question would do different things: Flamers would effectively replace the Meltagun Shotgun (leaving them to be precise heatwave armor slaying weapons) and be the natural rival to Assault Marines.. since you know.. they catch on fire and then burn to death whether in the sky or not.

Lore controversy aside, Nurgle's plagues are an integral part of the TT game where exposure to the warp infused microbes accelerates the ravages of plague to destroy its target in a matter of seconds. In fact, Nurgle's Rot was also not always a psychic power (I wish that it wasn't), and was treated in much the same way as a Chosen's Aura from WAR/Paladin's Aura from WoW, where if you were in range, you immediately began to feel the effects of it - the longer you stayed in that aura, the greater the effect. Which, in my mind opens up for some utterly FANTASTIC DoT's that are available to Chaos, making them stand apart from their loyalist brethern.

Nurlge: Simple and most damaging DoT Aura, causes you to move slower when active.
Khorne: Brass Collar Bloodboil - Has a strong negative effect against all nearby psykers. All attempts to cast a psychic power within range of this aura immediately receives a DoT of boiling blood. This effect
stacks.
Slaanesh: Psychedelic Stims A weak DoT that stacks on blind and concussive effects with every hit. Think a blind grenade effect from SM, the lingering after image of a flashbang from Cod, the Drunken State from WoW, and Shellshock/Supression from BF3 and then reduce it to about 2%, stacking on another 2% with every hit. Can be used in Bolt Weapons or Non-Powerfield weapons.
Tzeentch: Warpfire Bolts: Bolter Round hits cause the target to ignite and burn in unholy fire for a period of time.

That's obviously just Chaos.. The Eldar would also have fantastic and equally as brutal options... those robe wearing pansies....

Well considering Sorcerers will probably have quite a few things to choose from we will see allot of possible DoT variants (Nurgle mostly), but the examples given do good to make for some DoTs that could be attributed to non-psyker units (but not exclusive to them, a Nurgle Sorc would have no reason to be denied the DoT you spoke of above).

And Nurgle Rot (or Nurgle Rot themed spell) is a given going by what Brent told me, so im more worried on how to implement something that strong into the game without butchering it outright. After all the Rot is no laughing matter, and theres no cure for it.

I wonder if GW would allow them to dabble in making it curable, cause i get a frown each time i think someone would just brush off the Rot in a few seconds.