Hi,
on my experience on gf servers the following formula was nearly 100% perfect, except some randomnes. The gamepedia formulas are too old. after it was written, some changes on formulas was implemented in the several past years
Your chance to crit = ((('Your Critical Hit' - 'Target Critical Resistance') / 'Highest Critical value') + 1) / 2
'Your Critical Hit' is value from character screen (for example 7000)
'Target Critical Resistance' is Target Critical Resistance (for example 3000 for lvl90 mob)
'Highest Critical value' is the highest critical value of these (for
example 7000 is higher then 3000 so 7000 is the value we use)
Your chance to crit = (((7000 - 3000) / 7000) + 1) / 2 = 78.57%
Your own 'Critical Hit' is easy to find, its on the character screen
Your 'Target Critical Resistance' = 'Increased Critical Resistance bonuses' + 300 + (30 x 'target level')
Your targets 'Increased Critical Resistance bonuses' comes from honor gear, skills, etc.
If your target is a boss (not sure if it's also with none bosses) and
his level is higher then your level then his Critical Resistance gets a
bonus:
(('Target level' + 1) - 'Your level') x 650
So for example:
You lvl90
Your Critical Hit 7500
Boss lvl92
Boss Critical Resistance bonus 3000
Then our 'Target Critical Resistance' = 3000 + 300 + (30 x 92 = 2760) + (((92 + 1) - 90) x 650) = 8010
So your chance to crit = (((7500 - 8010) / 8010) + 1) / 2 = 46.82%
If you would happen to have a d/r with max rock slide and a wl/m wit max
Saces Cracking Spell in your raid then your chance to crit would be:
(((7500 - 5560) / 7500) + 1) / 2 = 64.47%
if you go with that same raid to a lvl87 boss who doesn't have any crit resist bonus then your chance to crit would be:
(((7500 - 230) / 7500) + 1) / 2 = 98.47%