I'd argue that is debatable.
1. ye it's not guaranteed to crit, but nor is lava burst guaranteed to proc echo (the chance that your stuff crits back to back is still higher than that lava burst procs echo)
2. I attempted to make a pic that explains how the globals works in WoW
The damage arrives within the time frame of the same global (since there is no travel time nor casting time), just like the damage of a lava burst that procs echo arrives in the same global. The difference is that chimera happens at the start of the global and Fire! at the end of the global (which is the same as the beginning of the next global). Or in other words: the second global starts after Fire! has done it's damage (instant aimed shot).
Edit: For an elemental shaman to do 105k lava bursts in iLvl 537 like the guy in your screenshot:
- he needs to play with unleash fury which leaves a debuff on you and a buff on him after unleashing
- or he needs tricks / clearcasting / trinket procs
Besides: clearcasting and unleash flame can be purged, unleashed fury debuff can be dispelled
Lava burst hits standard for like early 50k crit on a player target that has flame shock on it, without clearcasting / trinket / jade spirit procs and without unleashing.