CSS level 3 selectors: combining attribute selector and structural pseudo classes

Question

I have the following HTML:

<table>
    <tr>
        <td class="FINAL">The first cell.</td>
        <td class="FINAL">The second cell.</td>
        <td class="DRAFT">The third cell.</td>
        <td class="DRAFT">The fourth cell.</td>
    </tr>
    <!-- more rows with the same cell setup -->
</table>

I want to accomplish the following:

• The number of FINAL cells is variable, from 0 to unknown.
• The number of DRAFT cells is variable, from 0 to unknown.
• But there is always at least one cell (i.e. of either FINAL or DRAFT class)
• Adding an additional class to mark the last FINAL (as suggested in the duplication reference) is currently impossible.
• Must be a CSS-only solution.
• Select the last p element with the class "FINAL", and style it.
• Add a border between the last FINAL and the first DRAFT cell.

My naive CSS beginner's approach to this was the following selector:

td[class~=FINAL]:last-of-type {
    // CSS styles ehre
}

but that doesn't select anything except when I indeed have a FINAL td that is the last of its type in a table row.

https://stackoverflow.com/a/8539107/6000494 describes an interesting approach, but that doesn't fully apply here since I cannot guarantee that there will always be a first td element present.

SOLUTION:

The following selector does the trick (https://stackoverflow.com/a/33859457/6000494 pointed me to it):

.FINAL + :not(.FINAL) {
    border-left: 1px dotted black;
}

Update:

Edited the original description to a table context, which makes the suggested solution not work (AFAIK). Also clarified some of the constraints.

Update 2 The referenced question has an answer that - albeit not obvious to me - actually solves my problem: https://stackoverflow.com/a/33859457/6000494

A working jsFiddle demonstrates it.

Final update: Described the solution in the question. Can't mark the question as solved myself somehow...