The combo is a three skill combo where every skill helps to increase the odds of taking out an enemy player. The skills are claw, mighty blow, and piling on. Claw works by setting the target's armour to 7 if it was more than 7, which is +2 to armour rolls against most of my dwarves. Mighty blow works by adding +1 to the armour roll if needed. If not needed it instead adds +1 to injury roll. Piling on works by allowing you to knock yourself over to reroll either the armour or injury roll. How good are these things alone and in concert? I built a little chart containing the chance to at least knock someone out, as follows:
|Skills||7 AC||8 AC||9 AC||9 AC(ts)|
The table is laid out by armour value, with the last column indicating someone with 9 armour who also has the thick skull skill, which my dwarves have. Looking at the chart, piling on is actually the best of the single skills regardless of armour value, though claw is actually marginally better on a 9AC target without thick skull. For a 2-skill combo the best one against someone with 7 or 8 AC is mighty blow + piling on. Against someone with 9 AC it's claw + piling on. The full combo is more likely to KO+ someone than it is to fail to do so, which does seem pretty absurd. You're multiplying by 8.4 the chance of taking out someone with 9AC!
Piling on really seems like the best, so why is there only one copy of it in our league? Well, it does have some downsides. Putting yourself on the ground makes you vulnerable to being fouled, and it means you can't provide assists for the rest of your turn and the entire enemy turn. On the other hand it also means you can't get blocked or blitzed! Many people seem pretty reluctant to foul at all, which means putting your guy on the ground is actually the safest place for him. Falling down also means you have to spend the next turn standing up instead of blocking. I know my mental state put piling on in a category where I wanted to also have jump up, so I haven't even been considering it, but that is probably a leak in my game. Taking 3 movement to stand up is a big deal for my dwarves, though. Most of my team has 4 movement... Falling down probably puts that guy out of the play for a couple turns. My team is also built around massive amounts of guard, and having a guy with guard fall down is just terrible for me. That said, I do have a blitzer with mighty blow and +1 movement as his two skills thus far. Next time he levels, unless he rolls +1 agility, I think I should probably take piling on. And then do all my blitzing with him. I can never get access to claw, which makes me sad, but MB+PO is still a 58% chance at taking out a squishy dude! And since my guy has 9 armour and doesn't have guard it's not so bad if he falls down either. He's hard to hurt with a foul and I don't mind losing the tackle zone quite as much.
On a sad note my quarterfinals match will actually be against the one guy who has piling on. I'm considering keeping my Deathroller on the roster solely to foul that guy when he piles on. Deathroller has dirty player, see... And I don't mind if he gets kicked out. My cheapest player is 70k, so fouling out comes with a real cost to it for me normally so I try not to do it. But that one guy is more than 5 times as likely to take out one of my players than an unskilled dude, so getting rid of him seems important.