Originally Posted by
ChocoboMog123
Chaos Bolt gets +30% to its crit multiplier from Dark Soul, Shadowburn gets +30% chance to crit. Not gearing for Crit, I sit at about 30% crit rate with raid buffs, plus a significant amount more with trinket procs. You should have well over 50% crit rate during dark soul, which means those 700k Shadowburns will do more damage, on average than a Chaos Bolt, and in less than half the time (1 second GCD versus, say, about 1.8 second cast time).
Chaos Bolt becomes better DPET than Shadowburn at 103% Haste.
Chaos Bolt also gets the 20% full benefit from crit banner, whereas Shadowburn only gets your crit rate's worth of benefit. Even so, if you had ZERO percent crit (meaning Shadowburn gets no benefit from crit banner), you'd need 35% raid buffed Haste for Chaos Bolt to beat Shadowburn.
Basically, use Shadowburn.