Errata

The first strike tactic originally allowed for too many possible attacks in a round (as worded, the first striker can attack "each opponent " who enters melee range pre-emptively). This effectively puts First Strike on par with kits like Swashbuckler or Marksman, which grant additional attacks in the round. Fictionally what's happening is that you're attacking when someone enters range with a reach weapon, but it doesn't mean you get to attack them more times than you ordinarily would with them at close range. This incentivizes behavior that would align with what we expect someone with a reach weapon to do: sit back and wait to attack. First Strike is now revised such that you have the option to use your attack as a reaction against the first opponent who enters melee range in a round:

When the first opponent in a round enters melee range, you may make one of your attacks as a reaction against them. (This tactic does not grant you extra attacks.)

In this way, if I am a fighter and I have two attacks per round per Combat Expertise, I can use one of them pre-emptively when an opponent enters melee range outside of my turn, but not in addition to those granted by Combat Expertise. The attack is not made with disadvantage unless it is the extra attack granted by Combat Expertise.

Elsewhere there was some inconsistency in how the system handled edge cases involving Combat Expertise and parries. Previous rulings have been updated to respect the following:

1. The Fighter's Combat Expertise said in parenthesis that if the attacks are used as parries, then the second parry receives disadvantage. This is no longer the case. A parry is not an attack, even though you are rolling a contested attack to parry. The Fighter is unique in that he can exchange an attack for a parry, whereas all other classes have to take their action to parry. For this reason, the Fighter doesn't get disadvantage if they use their second attack as a parry.
2. Marksman, Swashbuckler, and Sellsword all apply disadvantage to the extra attack they grant in their own rules texts (this is for balance vs. the Fighter's Combat Expertise technique). Marksman and Sellsword allow you to spend MP to get extra attacks; Swashbuckler grants an extra attack as a reaction.

First Strike