I understand that the auction system was intended to be a pretty big gameplay mechanic, so here are my two cents on the issue with that in mind.

As an end-game player, I definitely have a lot more money than time at this point. I gladly overpay for things so that I don't have to sit there and babysit an auction.
But I'm not really a fan of the class system at all, especially since anyone can find big-ticket items and should be paid for those fairly.

But if you're wanting to encourage users to use the auction house over the user shops, I think limiting the types or rarity of items in there might help, as well as a limit on maximum price.
In my personal experience in early and mid-game, finding ingredients to make Evo-bars for my pets took potentially *days* for something I ended up paying like 10PC for at the auctions. (I just needed some darn blueberries!)
But if we could actually search and use user shops for smaller purchases like that, I think it would go a long way. By limiting items under a certain rarity and by type, you still encourage users to use the auction house.
Because if I needed some blueberries now, I'd just pop 150PC on that and call it a day.

Being able to host more auctions may help this, too. Because I only have 5 slots, I have to prioritize what auction I'll host and for how long. It's also just not worth my time anymore to host an auction for like 10PC, so I'm not contributing any items into the economy. I'd literally rather sell everything in my inventory for 1PC each just to avoid the hassle.

I think there should be a tax on user shop sales as well. Whether you want that higher, lower, or equal is up for debate.

That said, I'm a fan of most everything else proposed! That's just been my experience and I hope it helps to put things into perspective. :)