Attack rating decide how often you do your max damage range, instead of your minimum damage range.
The parry ratio of all of your defense items stacked, equals your chance to get dealt lower end damage, this will apply to what your enemy's attack rating is.
Hit ratio increases the chance of doing higher damage.
About the tablets don't know

EDIT: Found it
Focus: attack rating
Strikes: attack rating
Seems both add the same...
