It looks and sounds like you haven't really skipped any quests, and a grey exclamation point means the NPC will have something in another level or two -- but the ones down at that outpost (the one with goblins right, near the bug pit?) require level 45, so they should be showing for you.
This is the list of Tanaris quests, so you can check which you've done so far, in case there's one you've missed:
And you might check that you've visited Kelsey Steelspark up in Gadgetzan, she has some extra quests that seem to be easy to miss, starting in Gadget, then out on the coast where all the pirates are, then south of that outpost:
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