I 'think' their might be an overall stat cap of 999 via brews, but im not actually sure of that at all. It could just be 999 is the display cap like atk, even though it can go above it. This would only effect things when choosing atmas with brews, but otherwise there is absolutely no cap on stats like dex in abyssea.
Aanalaty, Mithra of San d'Oria
99Thf/99Drg/99Rng/95Pld/Secret Job 92
Maat-1/1 Thf Meleed (pansies steal)
Some of mah gearz: http://www.ffxiah.com/player/Lakshmi/Aanalaty#item-sets
Join 'People Against The Heart Snatcher' and help put Thfs on the right P.A.T.H.S.