It's statistical improbability/impossibility for bad chaos to roll even against the current metagame of BA being incredibly undercosted for the libbie/razorback. Even good generalship can only go so far, just as listbuilding can only go so far
Suck joy out of game with maths- check
When did people stop playing and start an in depth analysis of probability within the game?
To the OP, I like IoCG, it gives a re roll to a unit without fearless, which means they have a chance of sticking around which is nice and its only 10pts, which means you don't have to re write your army to fit it in. The best point about it is the re rolling of pinning checks, for those times when the rhino gets turned into terrain and you want to be on the other side of it. Personally I'd steer clear of the others as they are a touch on the pricey side for my liking.