Guild Wars 2

How much damage does it do?

2215 on a crit.

That is variable based on your character stats. Also take effects of down-leveling into account when figuring.

Wiki for it: http://wiki.guildwars2.com/wiki/Sigil_of_Fire

"The effect originates at the target with a radius of 240 and affects up to 5 foes."
"The flame blast has a 0.85 damage coefficient."

http://wiki.guildwars2.com/wiki/Damage
So:
Damage done = (Weapon strength) * Power * (skill-specific coefficient) / (target’s Armor)

As it seems to be direct damage, you should be able to see exactly how much your flame blast hits for in your chat tab if you have combat messages enabled on the tab.

Captain Unusual.9163:

2215 on a crit.

“The flame blast cannot critical hit.”
Wiki: http://wiki.guildwars2.com/wiki/Sigil_of_Fire

Also:

“Sigil of Fire: This sigil now has a 50% activation chance on critical hit. Damage is now reduced by 15%. Rescaled the cooldown from 5, 5, and 5 seconds to 9, 7, and 5 seconds for the minor, major, and superior versions, respectively. This sigil remains unable to critically hit.”
https://forum-en.gw2archive.eu/forum/info/updates/Game-Update-Notes-April-15-2014/3896042

This is the 0.85 damage coefficient (100% – 15% = 85%)

@Captain
Also stated there directly by ANet that it remains unable to critically hit.