I could speak at length about RF totems now.
They burn for 1/2 your life in aoe dps, and they burn the totem for 100% of its health per second. As a result, "Increased Burning Damage" is really more like "Increased Burning Rate", both for enemies and the totem you summon.
Since it takes 1s base to cast the totem, 1s base for the totem to cast RF, and it burns for 1s by default, you already need 100% cast speed with double totems to keep the fire continuous. For every point of burning damage increased you get, you'll need two points of cast speed to match it. On top of that, spell totem starts with -30 cast speed.
Like I said, more cast speed than you could possibly imagine. :P
And yeah, for damage, you're fighting for aoe, cspd, and +life on gear, and the best cspd/aoe you can get is on uniques without any +life. That hurts (except for Carcass Jack, which you won't have dex for). And unless you get a Kaom's, you're only going to be doing a few thousand base burn damage which isn't enough even with flammability+eleweak. Due to double totems, you can't even use Ele-equilibrium ice nova.
Double curse with flammability+eleweak helps immensely, but Whispers of Doom is too many points to sacrifice on the tree, and a Doedre's has no life or cast speed. That hurts.
Minion Resists support helps a ton since it makes the totem stick around longer, but it comes in as a 5L (after RF + totem + faster casting + increased aoe).
The totems are really hard to land since you have to lead an enemy ~1s in advance, and they will get instakilled by a sufficiently large ranged enemy pack at which point you just have to walk away.
Yeah, it's a failed build.
Here's what I was planning on: Tinderbox - RF totemancer. Before this I had Tinderbox as a Templar but realized it was 2 points inefficient.
He's currently level 51 on default and can't progress any farther into merciless. The damage is really low, which means later merciless and maps are pretty much out of the question. On the upside, the build wrecked everything through normal and the early parts of cruel (where player life is at its highest relative to enemy life).
A 5L Searing Touch or some other 5L with good cast speed (for RF + totem + faster casting + increased aoe + minion/totem resists, increased burning damage 6L if you can get the cast speed for it (which you can't)) and a Kaom's would make it merciless-viable. Would still probably suck in maps.
On the upside, the skill costs zero mana!