Dex doesn't seem to drop that much to me, and agi drops only when satisfied or burdened, or any combination of those states. So it is important to avoid being even satisfied, because it abuses agi. But anyway, it depends on each char, as I happen to have a character that trains agi fast and I'm around day 14 and it is always going up, right now it is 27, which is the highest I ever managed to have. This came very handy to kill Sherarax in melee, with no artificial limbs, pure melee, thought I could never do that. I just kept waiting to her to come right in front of me (pressing s to search) and hit her without being attacked by, then run again until I left her 1 tile behind, and press s again until she stepped forward, hit and run hit and run and.. that way I could kill her.
Also, it's amazing how Sherarax trains dex and agi, speccially dex, I brought 3 master necromancers to the level and she kept killing zombies one after the other and when I got a chance to sthetoscope her (she had only 1 leg) her dex was up to 120! Its almost double her original stats!