This is where you get it wrong.
The "normal" critical hit rules tells you what it takes to "score a critical hit."
This I do not disagree with.
This feature changes that and gives a new mechanic for how to "score a critical hit." It creates an exception to the "normal" critical hit rules.
But it does not create an exception to -all- the critical hit rules. And that is where you have made a mistake.
See, that 'exception' was already openned up and defined by another rule, Precision. Precision says that other features exist that break that normal rule, and of those that do, -only- a natural 20 is an automatic hit.
So here's where you have to examine the -full- hierarchy of the ruleset and exceptions that apply.
You need to beat their defense on your attack roll to hit that target, otherwise, you miss that target.
Rolling a Natural 20 will automaticly hit the target.
Rolling a Natural 20 will score a critical hit.
Scoring a critical hit does not occur when your roll does not hit the target. However, the automatic hit rule for a natural 20 does apply.
There exists features that allow you to roll numbers other than natural 20. Those numbers never automatic hit.
That's the way it works. Precision doesn't except how rolling a natural 20 works. It also does not except how the attack roll mechanics work.
Automatic hit is defined, it is the situation where the number you roll -should miss- but it is resolved as a hit regardless.
Holy Ardor does present an exception to the rule on what can score a critical hit. However it does -not- present an exception to the rule on what can or cannot hit the target. Therefore, you resolve it as tho all pertinent rules it does not except apply. Precision, furthermore, is a rule that tells you how to adjudicate these exceptions. That rule -itself- tells you what you do in a situation such as this. Thus, Holy Ardor has to -specificly- be an exception to -that- rule in order to work differently.
An example of this in action is the push mechanic. Let's say you have an enemy between you and a solid wall, and you have an effect that tells you to push him 2 squares.
Code:
[W] [ ] [ ]
[W] [E] [Y]
[W] [ ] [ ]
You cannot push that enemy a single square, and for no other reason than a rule -within the push mechanic- says you cannot do so.
Code:
[ ] [W] [ ] [ ]
[Z] [W] [E] [Y]
[ ] [W] [ ] [ ]
If you have a rule that instead says 'you may push the enemy to square Z' does that change anything? No. Because the rule for how a push works -still applies.- Pushing to a location is an exception to how pushing a number of squares work. But it is NOT an exception to the restrictions on how push works in the first place.
This is intuitive. This makes sense.
Changing the parameters of how an effect works compared to other effects doesn't necessarily change all the rules on how that effect works--it only changes the rules of that effect with regerd to the explicit exceptions.