TBC elemental resist plate

[Ynir]

Spangles, protection warrior, has the Enchanted Adamantite armor set, and the arcane resist ring, and neck. This gives 220 arcane resist, for whatever use it may be. She is the soaker for the Curator encounter, and puts it on for portions of heroic Mechanar.

She has all the other jewelcrafted resist rings/necks, figuring that they were put in the game for a purpose.

All her fire, nature, and shadow resist armor is old school, and needs upgrading. What is the upgrade for each, and in what order? I don't see need until Serpentshrine, is this correct?

Fire resist: Flamebane is a cheap crafted set that gives about 140 FR. There is an Inferno Tempered set that requires 100 heroic badges and gives 200 FR. Should we invest in the cheap set now, junk the Dark Iron stuff, and replace the cheap set piecewise with the heroic set? What level of FR must we attain? I hear 360 buffed is required now, instead of 315.

Wildguard Plate is a moderate cost set that provides 170 NR. Would one use this for tanking heroic Quagmirran?

Shadow, frost resist: same questions. What are the encounters that require them, and which sets provide useful levels of resistance?