I think Confession should be a daily power, which means you could balance it around being Melee 1 vs Reflex instead of AC. The ability could alternatively be a grab attack that requires you to maintain it until your next turn to Confess someone.
The grab attack maintained isn't bad, though a throat grab could be seen as normally are rather successful grab ;-), if we wanted to throw a penalty on it that seems reasonable too.
Kahlan gets her powers back in a few hours, not five minutes (more than a short rest, less than an extended one) and she is supposed to be the most powerful of the Confessors. Both the book (when relfecting about her 'sister', Denee) and the show cite examples about other Confessors being weaker and taking a day to regain the use of their power, so those characters might be better benchmarks when designing.
That bit about it being a daily is rather what I was saying... but her having something ie a feat which allows her more frequent use. Given the frequency or infrequency of combat encounters .... 5 minutes or an hour aren't functionally different the way I play.
Also assuming the others are npc's, or even minion class characters who almost always use the power outside of combat and not the heros that go on quests could also be a valid interpretation.
There is of course the power element as well. In the source material Confession is basically permanent and irrevocable, which doesn't work well with either an Encounter power, or even 4e's somewhat implicit concept that almost all effects end at the end of an encounter, but I don't really see a way around that.
Right...
There the Con Dar, "Blood Rage", that allowed Confessors to lash out with magical attacks as well as 'Confessing' with a look and no recovery time necessary. It was also only allowed to be used in defense of a friend, so perhaps an Immediate Reaction ability to an ally being reduced to 0 hit points?
right I had forgot about the Con Dar... but dropping to no recovery time... is one of those ouch Epic level things going on.
Here is the Sword of Truth wiki article related to Confessors which might be of help. Contains spoilers obviously, so read at your own risk.
Despite any of the work already done here on the class, I think a Leader designed along similar lines of the Bard would be a better fit for Confessor Lore for a full fledged class. Kahlan specifically was a wandering judge, diplomat, spiritual leader, et cetera. The Bardic niche of being versatile and knowledgeable across a broad spectrum of abilities would work well for the Confessor that stuck closely with the source material as well.
I don't think we are written in stone... remember after you take off the hunters quarry inspite of calling the class a striker.... the confessing.. is not a damage dealer to a great extent (but it takes out a single adversary kind of like damage.) so there is room to argue roles even in combat.
and you came up with the high level power ie a side from being able to reuse the power in defense of a single ally (is this a perhaps her combat role... a defender... her threat becomes the ability to mark everyone knows not to let her touch them).
In combat she doesnt come off as much as an inspirer or a tactician her out of combat role is distinct and yes leader like I think... we could pull in some out of combat class features perhaps like the bardic knowledge. This would be like here picking up a bit of nature skill training, figure she does that all the time with everyone she meets would be emphasizing the wizard created nature of her class knowledge is power after all.
I think giving her a fear power is kind of cool... even if in story its intimidation..if you can use it in a fight! it seems power like.
The armor of faith being in the picture is a little like that fear
having coherent effect in a fight too.
You could probably also work Confessor into a feat 'path' and Paragon Path, similar to the Student of the Plague from Forgotten Realms, or the smaller ones that have been appearing in Dragon Magazine for fighting styles (Chain Fighter, Bravo, et cetera). Kahlan specifically could be a Ranger or Rogue (the latter already having a solid reason to wield daggers) with Confessor feats. Considering the identity of 'Confessor' is built upon a single ability more or less this might be a better option than going through all of the work in creating an entire class.
A feat path and paragon path...Could you elaborate on how a fighting style type mechanic could be used? And what feats to lead up to the paragon path .
Giving up hunters quarry ie... replacing a core combat class feature seems needed don't think we can justify anything approaching confessing without that?... and if you do that don't you kind of need the higher frequency (kahlan is more of an adventurer build than the once per day types)
hmmm the character sure fights like an X with a single power tagged on, but there is so much out of combat difference calling her a rogue or various analog names would be rejected outright by anybody who wants to play the role. The order being created by Wizards with daggers being one of the classic wizard weapons would be an in story reason for her weaponry. I see the bard niche as you put it being in there.
Ah... I don't normally like much paragon paths that define a character as they are kind of like saying to a player I know you want to play this character but you are just going to have to be something different for awhile
however having "Con Dar" be a wait till epic class effect works for me.
In story the original confessor was just a wizard who gained a power ... but the resultant order seems a class in its own right. Perhaps we should take a wizard and replace magic missile with two weapon fighting daggers

= doubly not serious...