Still tinkering with TWF, still deep in the "add complexity 'til it breaks" phase. Next phase will be "cut back 'til it works." So, here's a slightly new approach:

— Mike Mearls, but Spooky (@mikemearls) October 24, 2018

I still like the idea of two weapons being the path of versatility at the cost of falling a little short compared to other options, so here’s what I have. When you use TWF you pick one of three modes: 1. Defense – +1 AC, attack as normal with one weapon.
2. Flurry – Make +1 extra attack but at a penalty
3. Focus Fire – attack as normal, but add off-hand weapon damage die to primary attack damage on all attacks

— Mike Mearls, but Spooky (@mikemearls) October 24, 2018

This is pretty sprawling, but at this stage in a design you’re just trying to figure out if the concept is distinct, fun, and flavorful. Basically – is there a chunk of people who see that and think, “That’s perfect for the character I want to play.” As it happens, I have two characters who dual wield in my campaign, so we'll see how this works. I think I'm done tinkering for now.

— Mike Mearls, but Spooky (@mikemearls) October 24, 2018

Mike, love what you’re tinkering with here, but I have a Meta question.

Say you land on something the community and WoTC staff agree is a winner; how does it get implemented?

“Option” in a future supplement? Errata? Another vehicle? Not likely a PHB change (as stated w/ Ranger) Most likely an optional rules module in a future product.

— Mike Mearls, but Spooky (@mikemearls) October 24, 2018

Any thoughts on allowing an off-hand dagger with a non-light main weapon? I like the image of the swashbuckler with a rapier and a parrying dagger Considering it – solving for two short swords first, then will poke at other cases

— Mike Mearls, but Spooky (@mikemearls) October 24, 2018

To me, two weapon fighting should be about flatening the bell curve. You attack more often. You miss more, you hit more. Attack penalties have always felt a bit off to me. This is an area where I envy video games, because you could easily imagine a debuff that triggers when you hit; if you miss you just follow up without penalty and get that consistency, if you hit you might want to ease off TWF for a moment as debuff cools down.

— Mike Mearls, but Spooky (@mikemearls) October 24, 2018