Valkyrie wrote:You don't multiply their attacks, you get two distinct rounds of combat, meaning you can attack once, your opponent then gets to activate a unit, then you can fight again.
This is not exactly true, or maybe I'm reading this wrong.
Red Butchers gain +1 S and can attack twice in a combat round. If they have charged, both of their rounds of attacks happen in the "Fights First" phase. So if the opponent has no one that can "Fight First", or does not interrupt, the Butchers (and Berzerkers) will attack twice before they can do anything. If the opponent does have someone that can fight first, then the Butchers could attack first (as per the rules), then the opponent would attack, then the Butchers again.
If you use the fight again strat, that happens at the end of the combat round, after everyone has attacked.
Do note that the +1 attack you get from charging as a World Eater only works on your first round of attacks. It give +1 attack per combat round, it does not increase your base attacks.
So a Butcher charging would get 4 attacks (2 base, 1 for angry marine, 1 for even angrier World Eater) their first round of attacks. Their second round of attacks and if you played the strat, those attacks would number 3 (2 base, 1 for angry marine, but no bonus for even angrier World Eater). It is a poor Legion trait that hopefully will be changed to match other +1 attack traits.