First and foremost, Christianity created sin. With this in mind it is up to the individual to determine what is deadly and what is not. But wait, on that note the people who are not christian still hold values don't they? Well, don't they? In fact they do not hold any values outside of what is pressured the entire life of a typical person.
Keep in mind most laws and ideas spread throughout the years of schooling and careers are usually based on the religious dominance in that area. Why are there few if any buddhist points being taught in school or in the workplace? Would it not benefit society as a whole more if everyone accepted one another and only followed what was comfortable to them? Apparently not according to the madmen who spread religious fear faster than they spread the religion itself.
Most people in our society are either christian or atheist, only a good fraction of other people worship differently. When I say christian I speak of ALL people who worship the deity known as the so called allmighty god of heaven. The same god who commands that his followers be his flock of bloodstained sheep; the blood being the result of gentle treachery unto others, as sheep do not kill with strength, they do it with a gentle touch of false beauty.
Now as for the sins themselves, what are they?
Lust-Strong feeling of desire for another person or object, can relate to promiscuity or to lust of a habit as a means of reliance. This occurs when the mental is becoming underactive, the emotional is active but imbalanced, and the physical is overactive.
Anger-A result of disagreement with something or someone else, can result from physical/mental/emotional
Pride-Feeling overconfident in one's own success or content. Usually results from overactive mind/emotion
Gluttony/Sloth-Desire to eat more than is naturally expected, to do what is less than expected. This can be seen as an underactive stimulation of the physical and mental.
Greed-To have or attempt to have more than others in some materialistic way. A result of overactive/imbalanced mental with an underactive emotional state.
Anger II/Wrath-To desire revenge out of anger or distaste for something. Forms from an underactive emotional a decently active mental, and an overactive energy from the physical.
Envy-Feeling spite towards another person or situation based on personal desire for what another person may experience. Envy shows up sometimes spontaneously, it is the result of an imbalanced active mind, decently active physical traits, and an overly active imbalanced emotional part of the mind.

Now at a glance these all sound rather undesirable but if that were indeed so then every normal human being would not perform such actions would they?
Each sin is natural and essential to human development. While a few things such as promiscuity as well as uncontrolled wrath are rather destructive when not given an effective outlet, they are still natural in that regard. It is natural to be angered, to desire, to want more, and to want nothing as well as to be proud of everything one has.
These traits are the founding principles of a generic mortal human being, it is the control and balance of these traits that lead a person into godhood. How can it possibly done otherwise unless a mortal experience every one of these? Each has a lesson to teach on the path to self discovery IF that is the desire of the individual, no one has to agree with anything I have mentioned, that is where the will must be seen. If these 7 things are seen as sins then that is the same as stating that wiillpower is a sin.
The responsibility of expressing the 7 so called sins is dependant on the person's actions; they create their own rules and vows,should those be broken it is based on their choice not on some malevolent force inspiring temptation. By no means are any of these so called sins even noteworthy of anything out of the ordinary, if anything every so called sin is probably experienced by most on a daily basis.
If we remember the diagram of the 7 main chakras, could we not give an equivelent to each "sin"?
Root Chakra: Lower body, physical traits/activity/-Sloth or Lust
Spleen Chakra: Mid lower body, healing ability/physical activity-Greed or Sloth
Solar Plexus: Central point of the lower body/Creativity/Auric energy-Anger
Heart Chakra: Crossing point of the body/emotions-Lust or Pride
Throat Chakra: Energy output and communication-Envy or Wrath
Third Eye Chakra: Clarity and mental abilities-greed or passive anger
Crown Chakra-Balance of the body, divinity-Any of the sins amplified
Keep in mind each chakra is an energy center, if one is overloaded or underworked it will affect the overall balance of the others. If a person is going to experience the "sins" of nature they should make it a point to create an outlet for such energies, creative or physical. Remember the rules a person has created within their internal mind determine how these actions will react within their environment, if you are bound to a rule you ahve created for your mind but go against it this will create in turn more stress on those chakras and those chakras of those around you.
As a conclusion, find outlets that will serve you as opposed to weaken you, many people write to filter out excess energy or to increase auric flow to underactive energy centers. As far as the dogmas surrounding the sins, they are part of being mortal, conquer and learn to control your nature and you will be as part god, and in time with patience would it not be possible to be a god entirely?