My point still stands even if I was wrong about OA
I wouldn't be faster in multi or single, it would faster based on the player doing the reaction. Some players take a long time to decide on actions, this slows down time while playing, add-on a pop up window for reactions and it stops combat and waits for the person to answer the box.
You would think people would be more inclined to reducing time in combat, not add more to it, guess not.
It's important to keep in mind what is a reaction, and most are not problematic at all.
- Opportunity Attack, an enemy needs to try to walk out of melee range.
- Absorb Elements: there needs to be an incoming spell on your character.
- Hellish Rebuke: an enemy has to damage your character.
- Shield: an attack need to be coming at your character.
- Featherfall: any character needs to be airborne and falling.
- Counterspell: an enemy has to attempt casting a spell
Might not make it into the game- Gift of gab: mostly for social, would be hard to implement in the game.
- Temporal Shunt: should be readied as well for the reaction.
- Soul Cage: an enemy has to die, it's also necromancy which may not make it into the game.
What is problematic, but not a reaction...
A paladin's Divine Smite, whenever they land an attack they can use a spell slot for Divine Smite. This is only a possible issue for the player playing as the paladin. And it should operate fine working as Hellish Rebuke currently is in the game, where the player preps it before hand, when they would want to use it.
The only reaction that might be an issue is Counterspell.
