Just chiming in to share some testing by a jp player on the "DEX=block?" subject.

http://lodestone.finalfantasyxiv.com...entry?e=260665

It's all in japanese, so some of the finer points may be missed, but it's quite obvious that boosting DEX did absolutely nothing for block rate. Block rate actually decreased due to the sacrifice of STR in some slots to stack DEX. I've personally seen a noticeable increase in block rate by stacking STR (albeit a small sample size).

Hopefully we get a dev response on how exactly they intend for these stats to work!