Well I disagree with you on that one Im afraid.
Firstly the water comes out of my tap at 5.2ish, so I have to use all that 'crap'.
I have kept Rift at 7.4 ph and yes they are fine, however, at 8 - 8.2 they are much more vibrant, the colours are brighter, the fish are more active, and they spawn more than at lower 7's.
Tangs need a very high ph, so 7.2 is way to low.
The salts add more than buffering capacity alone. They also aid the immune system of the fish, and keep them more disease resistant.
Epsom salts also make fish poo more, which helps keep the dreaded bloat at bay, and stops the fish becoming fat and lathargic.
Bicarb is a perfect choice for raising ph for a couple of reasons.
Firstly its cheap and readily available, secondly, it doesnt matter how much you add, it will NEVER raise the ph over 8.4.
Onto purigen...
Purigen was originally intended for reef fish, where purity is essential, however, for some reason Americans it seems, like to use it in Malawi set ups (I say American, because it is only on this forum I have seem people mention they use it)
Purigen takes to much out of the water for it to be used long term.
After a month of continuous use it effectively makes the water sterile, removing most trace elements, and starving the fish of many needed vitimins. which of course is why it is ok for marines, as many suppliments must be used for a healthy tank.
Carbon is much less corse, although it still removes alot, it doesnt remove the ESSENTIAL trace elements, and the trace elements it does remove, are replaced by the epsom salts at water change time!
If what you are comfortable with, is keeping fish in the wrong conditions, then you should change your tank inhabitants to a more suitable specimen, after all, keeping fish in unsuitable conditions due to your own short comings is cruel.