Replaces default attack meaning?

Grim Dawn Classes, Skills and Builds
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Grim Dawn - Game Guide

Passively Activated Weapon Skills
 Some abilities in Grim Dawn are passively activated on your basic attacks. The Soldier and Nightblade masteries provide several examples of this. Each of these abilities has a chance to activate, which is displayed as a percentage. What that means is that on every basic attack you do, you will have a chance of using the ability instead.

                      As you invest in these skills, their chance of activation  will increase. It is possible to get the total chance of activating  passive weapon abilities to go beyond 100%. When this occurs, all of  your basic attacks will be replaced by abilities and their chances of  activation will be used to determine their relative frequency.

This states that the default attack will be replaced by any passive skill that procs off of that attack.

I think this means that “Fire Strike” would be completely replaced by “Markovian’s Advantage”. None of the damage or skill attributes from "Fire Strike would be added to that attack instance.

I tried doing a search of a few sources for more information on this. I couldn’t find any concrete data on it though. I tried using the test dummies in game. I couldn’t really tell when “Markovian’s Advantage” had procced.

Any clarification would be appreciated.

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Im trying out a Melee Saboteur atm and using Fire Strike as main attack, works really great tbh, at lvl 55 now and just shredding through Elite.
All of the Nightblade procs are simply proccing on Fire Strike hits, as far as i understand this, their dmg is on top of the standard Fire Strike hit and dont replace it. At least the displayed dmg numbers looks for me like this. I only have 4 points in every %-attack from nightblade (dual blades line), so that each ability has ~20% chance to proc.