Seriously, it's proof enough that SE doesn't even know their own game.
Maxing DEX is 20% crit boost "only" so typically only 10% damage increase since it would probably only affect melee.
Maxing STR would be great if fstr didn't cap, however fstr caps at weapon rank + 8 so typically +20 fstr or +80 STR. Doing so your base damage goes from ~ 100 to ~ 120 => another 20% boost , to melee and ws this time.
Maxing vit means mobs will hit you with the minimum fstr, which is (wpn damage)-(wpn rank). Mob have much higher dmg than players. AV easily smacks you for 400-500 a hit, non crit. That's like 200 DMG ? remove 12 fstr and you get .. 188 DMG instead. So you take -6% damage ... all right ...?
Maxing DEF seems to be the most useful, so for you local PLD with 600 def that's ~ -40% damage taken
Maximizing attack does nothing or almost, because AV does not have very high def, it just have special form of taking less damage and a hgher level (pdif correction and -pdt). This and the fact that Dia III/minuet/chaos should be up and should cap you.
Conclusion :
How is gaining ~ 30%-40% damage output, taking ~ -45% damage, all of this during 3 minutes only, going to allow you to kill AV ?
What about meteor or aeroga4 followed by a crit ?