Destructive Perk / Critical Damage Cap.

[ɢǟɨƈɦʊ]

Does the effect "+50% Critical Damage while at max Rage" applies over the Critical Damage cap?

[datguy13]

Not unless you combine it with am enchantment/affix/Trophy Table effect which allows you to exceed the soft cap.

[ɢǟɨƈɦʊ]

there is a trophy that allows that? trophies drop like normal relics?
"affix" ?

[datguy13]

"Affix" is a term used for the blue colored text effects that you see on pieces of equipment that improve stats. Trophies do indeed drop like any other magic item, but the Epic versions which are needed to activate the Trophy Case effects are exceedingly hard to find until you stat doing high level Adventures. The "Poison Sack" Epic Trophy unlocks the ability to slot +5% Max Crit/+25% Max Crit Damage%.

[NoFoodAfterMidnight]

Anything that gives a bonus to the maximum of a stat, also gives that bonus to the stat. i.e. if you are at the cap of 500% crit damage, getting +50% max crit damage will just give you 550% crit damage. Same if you're at 200%, it will give you 250%.

So short answer, no, that perk doesn't give you anything if you've got maximum critical damage.