Brave weapons compensate for low atk too! They're just great weapons, they help everyone.
Of course they do, and the same is true of Killer/Silver. But the high-Atk options help low-Str characters more, and the heavy, double-hit options help low-Spd characters more.
For a case in point, here's Dhyerwolf's latest table reworked with the Kitchen Sink (typically Brave Sword/Lance, but also Light Brand / Hammer for Darin and S-ranks for Nergal). Also: Limstella sits on a +2 Def Gate (effective total 26), I am allowing the 15.8 AS Oswin to double the 12 AS Limstella and Kenneth, and these numbers include WTA/D where appropriate.
Sain/Guy/ Oswin
Limstella (12 AS)- 35.6/8/37.2
Uhai- (25 AS)- 33.8/16/34.6*
* Sain and Oswin are doubled (Sain is also 2HKOed), but Uhai can't counter melee, so no weapon changes
Kenneth (12 AS)- 83.6/48/85.2
Brendan (17 AS)- 31.8/32/30.6
Darin- (15 AS)- 35.8/20/18.3
Ursula- (16 AS)- 45.8/40/38.6
Jerme (18 AS?)- 31.8/28/32.6
Lloyd- (27 AS)- 19.9/12/36.6 *
* Lloyd 2HKOs and doubles Sain and Brave Sword Guy, so I assumed Spear and Silver Sword. Oswin is doubled too, but only 4HKOed, and sticks with Brave Lance.
Linus- (19 AS)- 29.8/20/30.6 *
* Assumed Linus' default Brave Sword for triangle purposes, but am ignoring its borderline 2HKO on Guy. (His backup is a Tomahawk.)
Nergal (13 AS)- 35.8/18/18.3
Average- 38.4/24.2/36.3
If you cap damage to Kenneth by his 56 HP, averages drop to 35.6/24.2/33.3. If you require 4.0 AS to double, Oswin's average drops to 30.1. Whatever your interpretation, this simple analysis ignores factors such as Hit and Crit which generally favor Guy, so I don't intend to say that it is proof Oswin > Guy or whatnot. But I do think it demonstrates that the issue's not as clear-cut as you may think.