Percent Chance To Hit
100 * ( Attack Rating / ( Attack Rating + Target Defense Rating ) )

Examples
AR: 25; Target DR: 50
100 * (25 / (25 + 50)) = 100 * (25 / 75) = 100 *  (1/3) = 33.3%

AR: 50; Target DR: 25
100 * (50 / (50 + 25)) = 100 * (50 / 75) = 100 * (2/3) = 66.7%

reference: http://forum.wildtangent.com/viewtopic.php?t=3881

Weapon Speed
Attack speeds range from .6 of the base animation speed to 1.2 of the base animation speed
Slowest: 0.6
Slow: 0.8
Normal: 1.0
Fast: 1.1
Fastest: 1.2

reference: http://forum.wildtangent.com/viewtopic.php?t=4332