A swarmlord over time will never on average hit that warlord with every attack. You need to read the rule book again to learn about WS and redo you math. You obviously don't know what the odds of four attacks at WS 9 are. You also fail to grasp how wounds work as well. Laughable, isn't it?

Wait what? Are you reading the words you are writing? I'm going to go ahead and assume you are drunk, in the same way I said 'Lets Assume he hits with all four attacks'

The only way it would cancel out is if you could re-roll a re-roll. You can house rule it as you want, but those skills don't cancel out. If they FAQ to say that they do, fine. It is no skin off of my nose, but until they do, streamlining it is not supported by the rules and are mathematically wrong.

If he passes all, his chances are 25% to pass again. If he fails all, his chances to fail all again are 25%. Whichever rule is invoked, it will follow. When you are statistically rolling 2 dice, those count.

Again i'm going to assume you're drunk, lets do this in baby steps for you.

Assumptions, The Warlock is fortuned, the Swarmlord hits with all 4 attacks. These are the base assumptions which have no effect on the probability of making an individual save.

The Warlock rolls 4 saves, 4 individual 6 sided dice. Probability states each dice has a 50/50 chance of passing his 4+ save on any one dice.

Thus he should pass 2 saves and fail two saves. He picks up his two successes and the Swarmlord makes him reroll them, should get one pass and one fail.

Fortune makes him pick up his 2 fails and reroll them, should get 1 pass and one fail.

End result, the chance of each save is exactly the same had no re rolls been made.

Lets look at what happens if the Swarmlord gets 1 wound, The Warlock picks up a dice and rolls it, no matter what result is rolled he picks up the dice and rolls it again. The probability is identical.

Aramoro