Reach Diagonals after the FAQ

[Scrawl Da'Wall]

I am aware of the FAQ ruling...

10-Foot Reach and Diagonals: I’m confused about reach and diagonals. I heard somewhere online that you don’t threaten the second diagonal with a 10-foot reach but that you somehow get an attack of opportunity when opponents move out of that square, but the Rules Reference Cards show that you do threaten the second diagonal. Which one is correct?
The cards are correct. As an exception to the way that diagonals normally work, a creature with 10 feet of reach threatens the second diagonal. These changes will be reflected in the next errata.

But what about those with longer reach..
Are diagonals essentially 5ft increments with reach weapons?

I have heard that they allowed the 10ft reach to affect the 2nd diagonal because it reaches partway into the square.

If so then you need 20ft reach for 3rd diagonal?

[Ascalaphus]

Beyond the second diagonal, and for reach greater than 10ft, use the normal distance measuring system.

This FAQ is only intended to patch weirdness that happened with medium creatures using polearms. That weirdness (a "gap" in threatened areas which you can step through) doesn't occur at bigger scales.

[Scrawl Da'Wall]

I think I found the problem. My Dm has been playing that EVERY diagonal after the first is 10ft. This was seriously detrimental to my reach build..

Thanks!

Sooo just to be sure...

1st=5' 2nd=15' 3rd=20' 4th=30'

25ft reach could reach into the 4th (30ft) diagonal?

[Chess Pwn]

No, 25ft reach cannot reach into the 30ft diagonal as it's too far away. Only the 15ft diagonal if you have 10ft reach was changed at all.

[Mark Seifter]

Chess Pwn wrote:

No, 25ft reach cannot reach into the 30ft diagonal as it's too far away. Only the 15ft diagonal if you have 10ft reach was changed at all.

This is correct. It works out though because a creature with 25 foot reach via pretty much any means in the game also can attack at 20 feet, whereas creatures with 10 foot reach can't attack at either 15 or 5, meaning they have absolutely no recourse on a diagonal.