I personally build all 4 of my RKs the following way.
Critical Rating = 17,000
Finesse = 15,000-20,000
Tactical Mastery = 50,000-60,000
Additionally the more tactical mastery you have the more damage your caltrops and bear traps will do in Big Battles
If you are in a T2/T3 raid I recommended
At least 10k in both physical and tactical mitigations
and 20 k morale
I normally keep 2 extra socketed armour with it the above in it to swap if I am needed in T2/T3
But here are the essences and what they do for tactical mastery
Minor Will = 116 Will = 928 Tactical Mastery
Major Will = 119 Will = 952 Tactical Mastery
Greater Will = 136 Will = 1088 Tactical Mastery
Supreme Will = 139 Will + 17 Vitality = 1113 Tactical Mastery, 51 Morale, 1 Tactical Mit
Minor Tactical Mastery +1053 Tactical Mastery Rating
Major Tactical Mastery +1075 Tactical Mastery Rating
Great Tactical Mastery +1229 Tactical Mastery Rating
Supreme Tactical Mastery +1229 Tactical Mastery Rating - +94 Maximum Power
With that being said I recommend tactical mastery