I would not necessarily recommend firing all tasks at once, because the Publisher will try to allocate each task to an available processor, and when it runs out of processors, some tasks might start failing. I'd recommend layering some of the tasks in time and not allowing more tasks to be released than the number of available CPU cores.
I'd either spread the tasks over time, or define dependencies between tasks that could ensure that one task doesn't begin before the other task is successfully finished.
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Similar suggestion to Oleg and similar cautions.
To gain a bit more throughput you could create multiple sets of dependent tasks. For example, you could define the task setup below (or something similar). Triggering the "Top Level Task" via EDX will result in each set of task dependencies below it executing concurrently.
Top Level Task
group 1: task A1
group 1: task A2
group 1: task A3
group 2: task B1
group 2: task B2
group 2: task B3
group 3: task C1
group 3: task C2
group 3: task C3