Sure but let's look at the Gladiator again.
Brute: A melee weapon deals one extra die of its damage when the gladiator hits with it (included in the attack).
What is the DM going to narrate to the players? That the Gladiator is a big mean bully and so does extra damage? What could the players do to counteract and avoid it? Not get hit?
The end result is pretty much the same- this guy is doing more damage because the game says so. The explanation doesn't really matter.
Lower the Gladiator's Strength by attacking him with a Shadow, subject him to a Slow spell, blind him, or affect him with fear, every time he makes a weapon attack, he does bonus damage. It's a "black box" with one moving part and no conditions attached to it.