Unfortunately, these Pieces are not too valuable. I had to learn this lesson, too - and I learned it in this forum: Mana Inc and Mana Reg is okay, because you cannot imbue it on a ring. SDI is nice, because it is capped at 12 with imbuing - so 3 more than usual. Focus and Luck, however, are worthless, you can imbue these properties easily and they don´t belong to the most searched after properties. So, the potential value of this ring is lowered by Focus and Luck.
Furthermore, the value of really great pieces derives from their usability for PVP. That´s why people search for SSI (+5/+10) or DCI (+20).
Even if some spellcasters would like to have a ring with Mana Inc and Mana Reg and slightly more SDI, you have to take into account that (a) most spellcasters imbue Mana Inc and Mana Reg on Armor and use Arties (esp. for Mana Reg), (b) this ring would be useless for PVP, and (c) most spellcasters search for jewelry with FC and FCR.
There are many posts about this issue and you might find the answers interesting which I got in similar cases...