I'm happy you replied with those particular questions, as I don't think I would have thought to ask them, and I like where thinking about the answers took me. Sorry I just only saw your comments tonight though. Below is a book I wrote in response to your comment/questions.
I view Alma 12:14 from the perspective of 1 Corinthians 13:12 "For now we see through a glass, darkly; but then face to face: now I know in part; but then shall I know even as also I am known." That when we are judged we will not disagree with that judgement but rather will, "confess before God that his judgments are just." (Mos. 16:1)
Going along with the idea that judgement is based upon what we become more than what we have done, I love how the above verses tie in wonderful harmony with D&C 76:94 "They who dwell in his presence are the church of the Firstborn; and they see as they are seen, and know as they are known, having received of his fulness and of his grace;" As if to suggest that to those who are "Celestial material" (though I hate that term) their judgement will not come as any kind of a surprise, at all suggesting a level of self-judgement.
To respond then to the need for an external judge, let me as a question: Can you, independent of any other instrument, weigh yourself? Independent of a ruler or tape measure, can you precisely tell your breadth or height? As a matter of philosophy (not that I'm an expert in that) it seems to me that any amount of judgement is based entirely on comparison. Any quantitative measure, whether it's things done or things become, is measured by a certain rule.
This is the point where I became excited at where this thought led me, because Christ as that yard-stick makes PERFECT sense. Christ being the Savior of all, the One who descended below all things, would have the only true measure of things as they really exist. Only a God would have a perspective universal enough in scope to determine what measure to use in each person's case. I want to point out by my choice of words that one could make a case again for self-judgement in bringing up 3 Nephi 14:2 For with what judgment ye judge, ye shall be judged; and with what measure ye mete, it shall be measured to you again.", but to counter, this passage is more Jesus informing his followers of how we are forgiven as we forgive, or in other words, how much his salvation can cover us, relative to how much we let it cover other people, thus making the issue again about Him, and not about us, his measure, not ours.
Which leads into your second thought of Jesus being both our Advocate and our Judge. To relate to this idea I was brought to a similar thought that I have carried since I was a teenager about how it seems from every seminary video I ever watched, that the Father and Jesus are playing bad cop-good cop with us. The one bent on throwing down hell-damning-justice, and the other sacrificing all making Himself a doormat to both the demands of justice and the offending unjust party. I outright reject the analogies (like the courtroom analogy) that make this appear to be the case. Rather, I see the Father possessing all justice and all mercy within Himself, and the Son possessing all justice and all mercy within Himself. These are not in opposition to each other, and God certainly isn't walking a tight-rope balancing act between them, or trying to juggle them all at once, but rather through the actions of the Son, both are brought into complete fulfillment.
One of my thoughts about how this is done (and how it figures in to judgement) ties into one of my major complaints about Mormons: Mormons have an over-developed sense of right and wrong! Mormons tend to think that if a persons sins it is because they are "bad". If this sinner then repents, they are "good", but if the person goes back to that same sin, they are "bad" again because they must have not really repented the first time. Though I do believe there are bad people in the world, they are so very rare, I think if we had a meter to judge good and bad people, we would be shocked at how few bad ones we would find. Rather, I think it would be FAR more accurate to say that for the most part, there are "strong" and "weak" people in this world. "A person who sins", says Elder Oaks, "is like a tree that bends easily in the wind and soils its leaves. If the Atonement were only to clean the leaves, the tree would be soiled again in the next high wind. Rather the Atonement is meant to strengthen the trunk of the tree, or the individual, giving them the stature to walk back into the presence of God." (an 85% accurate from memory paraphrase of his quote :-)
If then a measure of a person is strong or weak, it makes sin, and thus redemption and judgement, make much more sense. It makes the sermon on the mount where the Savior equates being angry with murder make so much more sense. Consider this: We as Mormons also like to talk about little sins versus big sins. To me, there are two elements to committing a sin: 1. Desire. 2. Opportunity. Taking murder as a 'Big Sin', I could be a murderer at heart, but I'm a skinny kid that would have a hard time even beating somebody up, so the opportunity to commit that big sin, or my perception of my ability to commit that sin, is null. Thus a person may be a murderer at heart, but have never committed the act. Interestingly enough (to me at least), the same weakness (whether mental or physical) that prevents them from killing someone, may also be the reason they don't have the ability to overcome those angry feelings. Who can judge what makes that person worthy or not? A God who can see the hearts of every other person ever born and use the summation of the universe as his yardstick.
What if judgement then, is more of an opportunity for Christ to compare you against the yardstick of perfect justice, and then apply His grace to allow us to be further strengthened, as I for one cannot conceive that I will arrive at my judgement already perfected. In that sense Christ becomes that fully just Master, and perfectly merciful Redeemer. In a recent episode of Community one of the characters tells the other, "Nobody cares if you're sorry, I want it fixed!". In that same way I see Christ in that role, not nearly as worried about how sorry we are for what we know is wrong with us, but what we (and He) are going to do to fix it. In this way my being judged by Christ is inextricable from my being saved by Christ.