I did a test against the first two brawlers in Iobar's Peak T2 level 100, looking at the damage I took from critical hits.
23,911 Physcial Mitigation (Capped at 61% according to character sheet)
22,808 Tactical Mitigation (Capped at 60% according to character sheet)
Weak Melee Attack (Common Damage): 646
Moderate Melee Attack (Frost Damage): 850
Minor Melee Attack (Frost Damage): 850
22,614 Physcial Mitigation (Capped at 61% according to character sheet)
17,709 Tactical Mitigation (Capped at 60% according to character sheet)
Weak Melee Attack (Common Damage): 669
Moderate Melee Attack (Frost Damage): 1072
Minor Melee Attack (Frost Damage): 1072
I took 26% more damage from tactical attacks with a mitigation value of 17,709 even though my character sheet still showed me at cap.
Conclusion: You want to be 6750 above cap to actually be at the cap in a T2 instance.