Group tasks by priority and apply.

orderTasks.js

function orderTasks(num) {
    var out = {},
    fib, i = 0,
    sum = idx = ct = 0,
    tasks = Array.apply(null, {length: num}).map(Number.call, Number).reverse(); // http://stackoverflow.com/a/20066663

    while (sum < num) {
        idx++;
        sum += getFib(idx);
    }

    for (i = 1; i <= idx; i++) {
        fib = getFib(i);
        out[fib] = tasks.slice(ct, ct + fib);
        ct += fib;
    }

    return out;
}

// Get n-th Fibonacci number where the 0th and 1st are 1 and 2nd is 2
function getFib(n) {
    if (n < 3)
        return n || 1;

    return getFib(n-2) + getFib(n-1);
}

Use orderTasks to group tasks according to priority.

Tasks are initially ordered sequentially by priority, so it suffices to provide the number of tasks. This function then divides them in priority groups, where the number of tasks in each group follows the Fibonacci sequence.

For instance, if 14 tasks are to be divided, this will be the final distribution (note the task number is 0-indexed):
1: 14
2: 13, 12
3: 11, 10, 9
5: 8, 7, 6, 5, 4
8: 3, 2, 1

Note that the last group (8) is not completely filled, because groups are filled starting from 1 and only go until there are no tasks left.