Searing Flames Math

[whowherewhat?]

Here's my attempt at understanding it :S please feel free to correct me:

I was wondering how many points one would have to put into the talent to make it worthwhile...such that the stacks will most likely not fall off.

So the talent: Causes the Searing Bolts from your Searing Totem to have a [20%/40%/60%/80%/100%] chance to set their targets aflame, dealing damage equal to the Searing Bolt's impact damage over 15 sec. Stacks up to 5 times.

Searing Totem attacks every 2 seconds, that gives us 7.5 attacks per stack duration (15 seconds a stack / 2 seconds per attack)

With 1 point in the talent, there's 20% chance a stack will be added on each attack: 20% chance to add => 80% chance to not add (duh). So for each attack in the 15 second window after the first stack is added, we have 4/5 of a chance not to add a stack. Probability-wise, this sets up a (4/5)^7.5 chance not to add a second stack, or 18.757575...% to not add a second stack.

Similarly, 2 points will yield a 3/5 chance not to add a stack, setting up a (3/5)^7.5 chance to not add a second stack over the duration of the first, or 2.168...% to not add a second stack

3 points is (2/5)^7.5 or .103...%
4 points is (1/5)^7.5 or .000572...%
5 is 0% of course.

In conclusion, I think that 3 points, with a chance of <1% to fail to add a stack would be the best amount of points to put into the talent. By not taking Booming Echoes, Thunderstorm, Wrathful Totems (and assuming a Demo Lock) one can achieve this (I would still take earthquake). 2 points still has a ~2.17% to not add another stack, which I think is pushing it. All opinion though, and my math could be wrong. I'm interested to see what others think of course :3
Edit: fixed wording

[macbethy]

(15 seconds a stack / 2 attacks a second)

right maths, but its 2 seconds per attack to make it 7.5 attacks a duration.

what would u do with the extra talent points?

[whowherewhat?]

right maths, but its 2 seconds per attack to make it 7.5 attacks a duration.

what would u do with the extra talent points?

Oops missed the wording there >.< I probably should have mentioned this was from an elemental perspective, its not feasible for us to take more than 3 without sacrificing from more important places in the tree (as it stands now). However, since 4/5 will give you a near-guranteed chance to add a stack I'd wager it isn't a bad idea as enhance to go just 4/5. I'm not sure where you'd spend the talent points though, I'm not versed in enhancement talenting

[Ajarma]

well I am curious now that you bring it up... how would this stand for Enhancment?

[whowherewhat?]

The intent of this talent, being in the enhancement tree, is probably to make you drop searing totem for single-target dps and magma for multiple target dps, instead of dropping magma for everything like in wrath