This passage does not imply that Jesus saw religious practice as irrelevant to an individual's ultimate fate. This is, indeed, a minimal situation. Consider the following:
1. An individual's ultimate fate is determined according to whether or not they are righteous.
Marvel not at this: for the hour is coming, in the
which all that are in the graves shall hear his voice, and shall come
forth; they that have done good, unto the resurrection of life; and
they that have done evil, unto the resurrection of damnation. (Joh 5:28-29)
2. God ultimately defines righteousness as faith in Himself.
And [Abram] believed in the LORD; and He counted it to him for
righteousness. (Genesis 15:6)
And therefore it was imputed to him for righteousness. Now it was not
written for his sake alone, that it was imputed to him; but for us
also, to whom it shall be imputed, if we believe on Him that raised up
Jesus our Lord from the dead; (Romans 4:22-24)
3. Faith that is genuine will manifest itself in action.
What doth it profit, my brethren, though a man say he hath faith, and
have not works? can faith save him? If a brother or sister be naked,
and destitute of daily food, and one of you say unto them, "Depart in
peace, be ye warmed and filled;" notwithstanding ye give them not
those things which are needful to the body; what doth it profit? Even
so faith, if it hath not works, is dead, being alone.
Yea, a man may say, "Thou hast faith, and I have works: shew me thy
faith without thy works, and I will shew thee my faith by my works."
Thou believest that there is one God; thou doest well: the devils also
believe, and tremble. But wilt thou know, O vain man, that faith
without works is dead?
Was not Abraham our father justified by works, when he had offered
Isaac his son upon the altar? Seest thou how faith wrought with his
works, and by works was faith made perfect? And the scripture was
fulfilled which saith, Abraham believed God, and it was imputed unto
him for righteousness: and he was called the Friend of God. Ye see
then how that by works a man is justified, and not by faith only.
Likewise also was not Rahab the harlot justified by works, when she
had received the messengers, and had sent them out another way?
For as the body without the spirit is dead, so faith without works is
dead also. (James 2:14-26)
4. The Scriptures reveal to us the actions that God Himself requires of us.
We call the expressed will of God requiring action on our part "the law."
All scripture is given by inspiration of God, and is profitable for
doctrine, for reproof, for correction, for instruction in
righteousness: (2 Timothy 3:16)
5. The laws of God are graded according to value.
Anytime we find ourselves in a moral dilemma (a situation in which two of God's laws require us to take contradictory actions), God expects us to follow the greater law. This is complex discussion that requires a complete consideration of multiple Scriptures, but here are a few instances in which a hierarchy of value in the law is clearly exhibited.
Samuel's words to Saul, when Saul offered the sacrifice instead of waiting for the priest, God's chosen minister of the sacrifice. Sacrifices were good, and had been instituted by God, but they had been instituted in a specific manner.
And Samuel said, Hath the LORD as great delight in burnt offerings and
sacrifices, as in obeying the voice of the LORD? Behold, to obey is
better than sacrifice, and to hearken than the fat of rams. (1 Samuel 15:22)
Christ's justification of David when David ate the shewbread in order to save his life and the lives of the men who were with him. The ritual laws were important, but not so much as the value of human life.
And he said unto them, "Have ye never read what David did, when he had
need, and was an hungred, he, and they that were with him? How he went
into the house of God in the days of Abiathar the high priest, and did
eat the shewbread, which is not lawful to eat but for the priests, and
gave also to them which were with him?" (Mark 2:25-26)
For that matter, Christ's healing of people on the sabbath (the point of contention He was addressing in Mark 2:25-26), in clear violation of laws against working on the sabbath is itself a demonstration that alleviating human suffering is more important than following the law of keeping sabbath.
And he saith unto them, "Is it lawful to do good on the sabbath days,
or to do evil? to save life, or to kill?"
But they held their peace.
And when he had looked round about on them with anger, being grieved
for the hardness of their hearts, he saith unto the man, "Stretch
forth thine hand." And he stretched it out: and his hand was restored
whole as the other. (Mark 3:4-5)
6. Jesus Christ defined for us the greatest law of all.
And one of the scribes came, and having heard them reasoning together,
and perceiving that he had answered them well, asked him, "Which is
the first commandment of all?"
And Jesus answered him, "The first of all the commandments is, Hear, O
Israel; The Lord our God is one Lord: And thou shalt love the Lord thy
God with all thy heart, and with all thy soul, and with all thy mind,
and with all thy strength: this is the first commandment. "And the
second is like, namely this, Thou shalt love thy neighbour as thyself.
There is none other commandment greater than these."
And the scribe said unto him, "Well, Master, thou hast said the truth:
for there is one God; and there is none other but he: and to love him
with all the heart, and with all the understanding, and with all the
soul, and with all the strength, and to love his neighbour as himself,
is more than all whole burnt offerings and sacrifices." (Mar 12:28-33)
Now, apply these given statements to the thief on the cross.
He had faith in Jesus' innocence ("this man has done nothing wrong"), in Jesus' authority ("your kingdom"), and in Jesus' ability ("remember me"). It is safe to assume, from Jesus' response ("today you will be with me in Paradise") that his faith extended also to Jesus' divinity - that He was, indeed, the Son of God.
His faith was demonstrated (action) by his speaking - and not just any speaking, but a vigorous form (he "rebuked" the thief who was railing).
Considering the fact that the thief was confined to the cross, he was in a moral dilemma. There were many laws that called upon him to act in many ways (one of which would have been to pay restitution for whatever it was he had stolen).
If a soul sin, and commit a trespass against the LORD, and lie unto
his neighbour in that which was delivered him to keep, or in
fellowship, or in a thing taken away by violence, or hath deceived his
Or have found that which was lost, and lieth concerning it, and
sweareth falsely; in any of all these that a man doeth, sinning
Then it shall be, because he hath sinned, and is guilty, that he shall
restore that which he took violently away, or the thing which he hath
deceitfully gotten, or that which was delivered him to keep, or the
lost thing which he found,
Or all that about which he hath sworn falsely; he shall even restore
it in the principal, and shall add the fifth part more thereto, and
give it unto him to whom it appertaineth, in the day of his trespass
And he shall bring his trespass offering unto the LORD, a ram without
blemish out of the flock, with thy estimation, for a trespass
offering, unto the priest:
And the priest shall make an atonement for him before the LORD: and it
shall be forgiven him for any thing of all that he hath done in
trespassing therein. (Leviticus 6:2-7)
However, he could not do any of those things because he was limited to only the actions he could take while restrained to the cross. So he was in a moral dilemma between the things he ought to do and the things he could do.
Therefore, the man was practicing religion as piously as any man who has ever been made righteous.
As to whether this is a minimal or exceptional situation: no exceptions were made for this man. He was/will be held to the same standard in the Day of Judgment as every one of us: "Did you love God with all your heart, with all your soul, with all your mind, and with all your strength?" The situation of the thief on the cross is a minimal one because the vast majority of us have far greater opportunities to obey the many laws God has laid out for us in His Word. Not many can truly say they are in the same moral dilemma that the thief found himself.