Had to look in the stupid skills.txt for the answer to this question. Mainly this post is to help myself years from now when I try to google this question up again. So, there are some random keywords at the bottom to increase my chances of finding me. Heed them no mind.
So I tried making a firewall Sorceress, and was really disappointed. Having to shoot sideways, being reliant on low-damage ice spells to pin trash mobs in place.. it really, really isn't the skill it used to be in Diablo 1. In that game, the wall had TWICE the depth of this... weenie thing.
So, respeced into Meteor instead. Did I mention I love the new respecs?
Now, Meteor has a fire over time component. Like many, I disregarded it as pitiful and meaningless in the long run. However, I noticed its duration with skill levels skyrocketed over time. Must have been a change sometime after they added timers to skills. Harumph.
So it's 30 frames long, with another 15 frames per skill point. That's +.6 seconds a point.
And what does that mean for Fire Wall? Most pessimistic numbers for Meteor's duration (as I don't know whether the first point gives you +.6 seconds), we have:
Meteor/Inferno 20/Fire Mastery 20:
At 20: 16858
Fire Wall/Warmth 20/Fire Mastery 20:
At 20: 22291
I'm far too lazy to calculate the level at which Meteor over takes Firewall's damage, boy am I lazy, but it happens eventually.
So Firewall has a longer cast timer, has a crazy thin spread out AoE, and eventually causes less damage than Meteor. On the flipside, it doesn't make you wait four seconds before eating at monster's health, and Meteor's fire takes ~20+ seconds to run its course. Which is an eternity in retrospect.
All I know is I wish Firewall would get a little thicker with levels. And having 14+ meteors burning at the same time shows they're full of poop when it comes to gimping Immolation arrow's ability to stack.
Meteor fire duration
Duration of Meteor's fire
Meteor Fire Length
Length of Meteor's fire
Why isn't this on Arreat Summit.com dammit