It's a sound logic and it's true that you weaken the factor of the dice. But mathematically, in this model anyhow, that isn't reflected at all.
I'll explain why this is so... But there's a TLDR version below. Also, we're reaching a slightly sketchy level here. This is something to keep in mind, but will rarely serve tactical choices (It's more useful for the game designer).
The long explanation
The mathematical term we need here is the "variance", which is calculated as follows:
variance = n * p * (1-p)
* n is the number of attacks
* p is the chance to kill.
We can plot this in a graphic, for different numbers of attacks (10, 20, 30) and different chance to score a kill.
We see that:
- The more attacks you have, the bigger the variance will become (you have more potential outcomes). In fact, it increases dramatically with the number of attacks.
- The variance increases as your chance on a kill approaches 50%.
This second revelation is a little less intuitive at first, but follows sound logic:
- if your model has very little chance of scoring a kill, well, then it's reliably going to fail.
- if your model is making every attack a success, then it's reliably going to kick ass.
- Anything in the middle is subject to more randomness.. (In an even matchup in football, the outcome can swing either way).
Strength 3 attacks will rarely make a very killy character. Just imagine a 3+ to hit and 4+ to wound which yields 33% chance to wound per attack. Any armor, ward, higher toughness or higher weapon skill is going to weaken that chance. As your chance decreases, you go further away from the "50%" peak in variation and your unit becomes more reliable. Witch Elves, thanks to poison, crawl closer to that 50% and only pass it marginally in some situations. That is why they will usually have more variance than frenzied Corsairs.
If the Corsairs aren't frenzied, then the Corsairs are far less subject to variance because both their chance to kill is lower and their number of attacks.
Executioners swing the other way: against common infantry they have well over 50% kill chance per attack and become more reliable in killing power. They also have notably fewer attacks, which makes their variance lower. (Well, when you have only 10 attacks, it can go only from 0 to 10 attacks. If you have 30, it can go from 0 to 30.)
TL DR
Witch Elves are the most random, simply because their killing power per attack is right in the middle lane and they throw in an incredible number of attacks. This makes a lot of outcomes plausible.
Corsairs are "reliably" weaker, making fewer outcomes plausible. Without frenzy they have fewer attacks, further reducing the number plausible outcomes.
Executioners are very killy per attack and have a low number of attacks. This makes their performance less random, but not necessarily better.
It could be reasoned this is part of the value of a character:
- Few attacks (limited number of outcomes)
- Very high killing power per attack (making the attacks reliable)
So it adds reliable killing power to a unit, which is never something to be sneezed at.