There's no way to preview them directly, but 90% of the Epic powers and many of the Patron powers are powers available to other archetypes in their primaries and secondaries, so you could make a new character with the appropriate sets and skip to the Powers tab in the character creator to get a sneak peek at some of them.
Issue 16 made me feel like this.
Warning: This poster likes to play Devil's Advocate.
Is there any place where one can preview the power animations for the Epic and Patron sets before designing a character? I thought I might be able to find them on the Titan Wiki, but either they weren't there, or I couldn't find them.