Cold/Fire Defender
If you're worried about mitigating damage then consider taking Mace Mastery for Scorpion Shield. It'll boost your S/L/E defenses, the three most common damage types.
Sounds like a lot of fun; you could probably see some ridiculous numbers going Sleet -> Heat Loss -> Inferno, and if you tag enough mobs you'll have recovery through it as well.
I took a Cold/Sonic to 50 recently, although I took Dark Mastery to build on stuns in the secondary. I figured out faceplanting isn't as big of a worry when you can get back up every ~2-3 minutes, and get a mag 30 stun & 10 secs of untouchable in the process
Ooh, I hadnt thought of that! Does Heat loss potentially provide enough recovery to overcome the post-nuke penalty? I'd been planning to skip Inferno, maybe not...
I've been looking at the numbers for rain powers in Red Tomax and they seem a bit odd.
Ice Storm does the same damage for Blasters, Corrupters and Defenders.
Rain fo Fire does the same damage for Blasters and Corrupters, but about 65% for Defenders.
Did the devs give Defenders a special Defender-scale pet for Rain of Fire? If so, its abit odd that Defender Ice Sotrm now does more damage than Defender Rain of Fire.
And if this is right, it may be enough to make me roll this character as a Corrupter instead. But then I have to wait till 35 for Sleet, and the shields are poorer. Decisions, decisions...
Can anyone confirm this about Defender Rain of Fire?
re: heat loss, slotted properly, if you can tag 8 enemies, you should get 1100% or so recovery. You'll get random toggles dropping depending on your luck, but usually some stay up. (Heat loss end recovery scalars are the same for both corr and defender, so either way you go, you should be able to have fun.)
I deleted my cold defender because I wasn't feeling strong enough with her, but cold/fire sounds fun I love interesting combos
Defender RoF unslotted @lvl 50 = 76 x 1.11 fire damage
Corruptor RoF = Blaster RoF = 76 x 1.67
Playing CoH with Gestures

Thanks for that second opinion, Dr.
I've decided to go with a Corrupter for the heavier scourging Rain of Fire, and will just have to tolerate the wait for Sleet until 35. Should be an interesting ride - like a Blaster who can boost team survivability, but not my own so much.
I've had a longstanding problem with getting a Cold Domination character off the ground, and think this combo may solve it.
It looks on paper like a highly offensive team Defender - buff your allies, let them go in first, then melt everything with the double rain of Sleet and Rain of Fire.
Its fairly low on personal damage mitigation - Cold's best buffs are allies only and Fire has no mez powers - so the best solo tactic would appear to be to take on lots of lower level enemies and use the rains, Snow Storm and other AoEs to melt large spawns.
Has anyone else tried this combo?
Would it work better as a Corrupter? Rain of Fire seems to give lower damage for Defenders but Blaster levels values as a Corrupter according to Red Tomax. Is that right? I'm loathe to go Corrupter purely for the 9 levels difference in waiting for Sleet, but a large enough damage difference could swing it.