Assume a Player Character in a heavy metal armor gets attacked by a diabolist using the Debauchery/Effusion Effect "Lucifer´s Tongs" (described in "Tales of Mythic Europe", p. 142: for the duration Diam. his armor becomes red hot and causes +6 damage per round, if the character touches the metal... and I think, he does...). In my opinion it takes longer than two minutes to strip off an armor. What can the character do, to prevent 20 rounds of +6 damage?
Remember that metal armour has considerable padding underneath it to make it wearable and so not all of the wearer's skin is in direct contact with the metal. You could allow a resistance STA roll to mitigate some of the damage each round.
Assuming, that is, you want to be fairer to your PCs. If you want to be nasty to them, then BBQ them!
Also most metal armour is rather easy to get out of (depending on how much you have strapped on outside), specially if you don't much care about being careful not to destroy it or harming it.
With only a belt I can get out of full chain in far less than 30 seconds (you basically just drop the belt, hitch up the bottom to the waist and bow forward and it falls off. Fast. This also works with a tabard on, with no delay)
If you are wearing metal (plates or rings or shells) strapped to leather it is a bit harder, but the padding and the leather should have you rather well protected from the start so you should have some more soak and/or more time before it gets serious. If you are thinking of plate (which I think is out of period, but cool) it has the same situation, but far more metal to heat. Getting out of the metal parts of these kinds of armour isn't too hard if you don't mind having to repair it afterwards. Most hard armour is strapped on with leather straps or even tied on with laces. With a good knife and/or serious motivation you can cut yourself out of it rather fast.
Finally you shouldn't be in much (if any) contact with the metal of your armour if it is properly put on. You always want padding and clothing between the outer metal and your skin and body.
SO: if the heavy metal armour is a full chain it should be easy to get it off in 2-4 rounds (depending on how much you have on in addition to the armour and wether you are wearing just the long shirt and coif or have trousers in addition). Getting it off will leave you totally vulnerable, but still be the best way to get away from harm. If it is some sort of hard armour you should cut straps and laces and get out of it, but probably not as fast. Your padding (which is not metal, thick and always on) should protect you from a bit of the harm, initially.
Yeah. Getting out of armor takes a lot less time than two minutes if you're in a hurry. Getting into armor takes a while, but most of that is adjusting straps and making sure the various bits go where they're supposed to.
I'd say a person could probably get the metal bits of their armour off in 3-4 rounds - provided they don't mind just flinging it off. I'd also say that the metal armor would take ~1 round to start doing damage through the padding - during which time the wearer would know full well that it was hot. So if the wearer takes immediate action, you're looking at having to soak ~2-3 rounds of +6 damage - which is much more manageable. Of course, it also means the victim isn't going to be doing much else for those rounds and will be bereft of their armor soak afterwards. Pleanty of time for the diabolist to do something else nefarious. Or run away.
I´ll use stress dies with decreasing ease factors for getting rid of the armor.
One word about the padding...
The spelldescription "Heat of the searing flame" (CrIg10) discusses the problem: "Most metal armor has leather or cloth underneath that gives the victim a +3 Soak bonus against the heat."
"Lucifer´s Tongs" contains no comparable passage.
Is the adjustment of the spelldescriptions a bit superficial (then you could assume a similar rule for padding concerning both spells) or would you call this an intentional difference (then "Lucifer´s Tongs" works somehow different than "Heat of searing flame")?
+1. When you write you usually have a word count. Authors ALWAYS go beyond that word count. Heavily. Reducing word count is a pain in the ass, so if you can do it in places like this one where it is not a big problem, much better.