Don't worry about the Dragon thing on Crimson Cuisses.
A Fire resist set is pretty much all or nothing, if you can't hit the magic number to get a 90-95% resist rate, you're better off just using a MDT/MDB build.
The magic number for Tiamat is believed to be over 300, maybe 320 (I don't know, only fought him a couple times helping a friends HNMLS late at night and I'm over 320 with support), whereas the KS99 Wyrm needs far less, I've heard 200 and 250. (Again not 100% sure, I just use one set for both fights)
You should plan this out with your WHMs and BRDs, make sure the BRDs have an HQ Crumhorn and the WHMs have a Barspell setup, then you'll know how much in gear you need to reach the proper resist rate.
Assuming full IR, you'll get 30 there, and you can get enough in other slots IF you have pretty much the best of the best everywhere else (Talking for Tiamat), you can do a set that entails the full IR armor.
For the KS99, you can probably use full IR and other slots with a good amount of Fire resist, but again it depends on what you have access to and your BRD and WHMs.
I find it's much easier to use a set that doesn't rely on any IR gear to hit enough resist. You're taking such little damage anyway that you're not losing much CE, so the Enmity from IR is only marginally useful, and the MDB, while neat to take single digit damage all the time if you can get away with it, isn't doing nearly as much as ensuring that you're resisting at the full %.
Although now, I might use an IR set for the KS99, looking at it I could hit 127, plus 50 from Carol, and I have 2 WHMs in the LS with full Barspell setups, I think I'll try it. Be nice to offload that Breastplate and have that money for something else.
It's late, I'm rambling, I'll probably read this in the morning and edit it for clarity.
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