PLS help me compute the odds!

Because you've made all the averages the same, these units will all effectively be equal when matched against each other.

There is a 50% chance of rolling higher or lower than average in every case (obviously) and just because the range on either side of average is different, that doesn't make one unit better than the other.

The only way the the higher value units could be more valuable would be if rolling close to the average result was good. E.G. If a roll of 7 or 8 is a critical hit and the further you are away from that, the worse you are, then the higher value units are stronger because they roll those numbers more often.

In the example of a 1 vs 5 fight, there is a 4/48 chance of a tie (i.e. 1/12 or 8.3%) and an equal 45.83% chance of either die "winning".

This is calculated from there being 4 x 12 possible outcomes, meaning 48. Of these, 4 would be the same value on each die (4/48), 22 would be die A being higher and 22 would be die B being higher. You can write out all the possible outcomes on a piece of graph paper or a spreadsheet; here's a link to a Google spreadsheet I put together to illustrate the point:

https://docs.google.com/spreadsheets/d/13M8r66Wji9wHJhUgsvZ43b_qlx-bw27b...

Ties going to the defender does make a difference, yes, because then there are no ties. But the chances of a tie are the same between any pair of dice, regardless of who is the attacker, and who the defender. i.e. in a 5 vs 1 scenario there is a 1/12 chance of a tie, no matter which die is the defender.

It's worth noting that ties would occur more frequently if the dice are both smaller. i.e. two D4s rolling off will tie 1/4 of the time whereas two D12s will only tie 1/12 of the time.

In any case, yes, I am saying that all of these are effectively equal, if we assume they all act as attacker and defender as much as one another.