I seem to remember the str/dex removal from parry was from patch 2.4X or 2.5X. The main reason announced at the time was because stat allocation was "too confusing" for new players when playing tanks. Tanks were presented with a choice of allocating points in 3 different stats affecting your tanking ability, while other classes didn't.
Keep in mind one of the goals of the game is to make it accessible to new players (including players new to the MMO genre) and they tend to do that by removing choices (because you know, choices = difficult).