Updated Monster Knowledge Checks say Powers on Hard DC
The current online compendium entry for Monster Knowledge Checks states:
DC: The DM sets the DC using the Difficulty Class by Level table, selecting the moderate DC for the monster’s level instead of the level of the character making the check.
Success: The character identifies the monster and knows its origin, type, typical temperament, and keywords. If the character meets or exceeds the hard DC for the monster’s level, he or she also knows the monster’s resistances and vulnerabilities, as well as what its powers do.
Traits are a subcategory of keyword, if I'm not mistaken, so you would know traits on a Medium DC check along with the other basic information. Traits include movement modes (eg: Earth Walk) and whether or not a creature is a Mount, for example.
Although the entry for Aura doesn't say anything about powers, the entry for Aura is under the category of Powers which suggests that Auras are powers and players would know about Auras when they learn about powers on a successful hard DC knowledge check.
Note, however, that the DCs are not the fixed values you listed but variable, depending on the monster's level. The Skill Check Difficulty ClassDDI table has Hard DCs range from 19 to 42 for monsters level 1 to 30.