How is it fair if a less active person had the highest bid on a godly item that drops once in a CH lifetime?
It's fair because the person isn't less active if they have more points. If they already spent them our clan handles this by turning in items and returning points.
How is it fair that different people may pay different amounts for the same kind of item because there was no bidding war?
Its fair if it is due to supply and demand. Being the first to have an item has its costs. If people are running up bids with no intention of using then that is a clan morale issue that goes beyond dkp.
How is it fair that the person who has the most points may not end up with the most items (or even the best ones)?
if they don't end up with the best items you are doing dkp wrong, the whole point is points win all.
Such are the massive flaws of a bidding/auction system.
Yes there are problems but the above aren't always so bad.