I have a Warlock who's up to L6, but I haven't seen any Artifacts skill to add points to so I can identify items. The Warlock was previously an Oomphaz Wizard.

I have a 6th level Priest Whiskah who was offered the Ancient Lore skill at 3rd level-up, and the Artifact skill at the 4th level-up. Is this usual? He can only identify silver rings and gemstones at this point at Artifact 1, but I thought only Warlocks were able to identify stuff. Not complaining at all though.. hehe.

There may be other skills you need as you go up the guild ladder (don't ask, I just go for new skills, within reason). One skill may lead to another skill opportunity. Also, artifact (or whatever it takes) skill has to be at 5 or 6 to identify the good stuff.

And, BTW, my Oomphaz is a warlock (cuurently) and does all identifying (level 11)

If I remember correctly, you have to reach membership level 3 at either the League of Sorcery or the Priests' Guild in order to learn Artifacts. So... complete your quests for the guild. (I imagine you're still at Valeia). The Priest guild has easier quests, so make sure your Warlock joins it.