I rolled a Devoted/Berserker who can stack 100% hit-to-crit conversion via Frenzy + Disciplined Strikes, yet I still landed a regular hit in combat:

 

 

However, the UI never communicates that either effect is suppressed:

 

 

Besides, they come from a different source and have different wording (one applies to all attacks; the other only to melee weapons) so all points toward their stacking. The expected behavior is that all hits are converted to crits for the duration, and simply hitting should be impossible outside of graze conversion.

Mmm interesting, maybe the chance is multipled instead of added?

Or maybe its two chances to convert the hit to a crit as in you roll for the first 50% check and then roll a second time to check the other 50% check?

 

Regardless it needs to be clearly listed somewhere as to what should or should not stack so that we can look for mistakes.

Or the target has something like PoE I fighter passive ability Critical Defense

Self: +20% of incoming Crits converted to Hits
Self: +10% of incoming Hits converted to Grazes

Just maybe...

Or maybe its two chances to convert the hit to a crit as in you roll for the first 50% check and then roll a second time to check the other 50% check?

I think that's exactly what happened.

 

The status effects are different, and were processed separately, resulting in 75% hit-to-crit conversion with weapons, and 50% hit-to-crit conversion with anything else.

Again: very transparent mechanics with a PoE game...

 

Watch out! Ironic post!