So the transition of TaskGroup to ES6 is complete (pushed but not yet published).
The CoffeeScript TaskGroup executed 50,000 tasks in 13 seconds, the ES6 TaskGroup did it in 8 seconds, with optimisations it went down to 3.5 seconds. This is in the browser with domains disabled.
Applying the updated TaskGroup to the latest DocPad, the largesite generation of 1000 jade files with a single layout went from 65 seconds with 500mb of memory, to 48 seconds with 350mb of memory. With domains disabled, it goes down to 40 seconds with 300mb of memory.
I'll do some more reviews of this, and see what else can be done. @pflannery thanks for your efforts on this, keen to hear your thoughts too