Chance to Ignite

burning damage is always 133% extra damage based off the fire damage delt (except with burning damage boost passives), in no way is it weak on its own. of course crit based application is better, crits are flat multiplier damage.

burning arrow already has chance to ignite so either have 30% extra fire damage, or 30% chance for multiplying your damage delt. weapon elemental support is smart, boosting fire even further and this also burning whenever burning arrow procs. fire penetration is just as valuable as weapon elemental damage, less res the foe has, the more damage both fire and burning does.

Well, I currently do a BA Templar, and I certainly intend to use RT and Chance to ignite.
I'll miss the added fire damage, but I suppose a decent Blackgleam (There's still rumors about a new AoF) adds enough fire damage for burn.
Yes, for pure dps/bosses, I'd probably take out ignite and proliferation and insert added fire and another damage gem.
With some burn duration and burn damage bonuses, I think 250% of fire damage as AOE burn is doable; not necessarily weak.
Sure, it might not reach D2 Plague Javelin, but it's workable.
DoT builds are per definition never about killspeed.

Well, the Fire Penetration is really all you need.
On reachable levels, it reduces enemy resists (unless they have high level Purity support) to a maximum of 35%.
That's actually pretty bearable.
In that case, I'd prefer Vulnerability, as I can stack it with a Poison cloud for double the fun.

to get that low, someone would be using both (fire pen + flamibility) or all three(add ele weakness), maybe somehow also EE but thats going a bit silly.

lv 16 of all three reductions is -130% (or 40 +45 +45). so either -30% res for mobs (guessing hardest mode uses 100% res) or -130%. which translates to 1.3 times fire damage or total of 1.69 increase for burning and 2.3 times fire damage or 5.29 total boost to burning. i'm starting to think burning isn't affected twice by res.

Thr problem is that merciless fire resist mobs may have up to 125% resists, of which only 75% weight in.
Fire penetration ignores those excess resists, -35% resist still ends at 40%;
Using Flamability and Elemental Weakness for an 80% reduction will cost a significant amount of mana and time, for just 30% less resistance, when that investment could be used for Vulnerability (more dot, would stack with flamability) or just killing the targets with more fire damage.
Or any other damage.

The point is, if the mob has 125% fire resist, with 75% effective, and you cast Curses worth 80% less resist, the target will end up at 45% resist, or close to 0 with penetration.
Penetration alone will already bring it down to 30-35%, and save you a huge heap mana with which you can add a poison arrow or just shoot more fire; Curses are expensive.
Or you use a secondary skill, if you go as far as having two high level curses and the equipment to stack them, you might as well just have a secondary spell of another element to use instead.
Also it's worth noting that while against resistant mobs, stacking resist drops is the best, against enemies where penetration alone results in 0 resists or lower, Vulnerability would have a greater effect on burn damage, though not on initial damage and thus not on total burn, as well.
Vulnerability would have that effect with puncture, though.

How did we even get to this discussion?
0.o