I don't think he's lost any steam at all, personally. Not being the most memorable person or character in a film doesn't rank how good that actor is, or how good the actors choices are. If Bale was the most memorable character in 3:10 to Yuma, The Dark Knight, Public Enemies and Terminator Salvation, he wouldn't have done the film he signed on for justice and this thread would be "Has Christian Bale's Ego Exploded?". Bale's as good as he's ever been as Bruce Wayne/Batman, but the film is rightly centered around Dent/Two-Face's arc, and memorable because of Joker, because it's what services the film best. Bale doesn't stand-out, but his performance is solid. Terminator Salvation was a mis-step, in my opinion, wasn't a big fan of Bale or Worthington's performances (Yelchin needed more screen-time). Again, like The Dark Knight, Bale's performances in 3:10 to Yuma and The Prestige fit the characters and let the more flamboyant character take the spotlight, which was right for each respective story. Bale's scenes with Crowe are brilliant in the film, and his performance in The Prestige is better than Jackman's (in my opinion) - I much prefer the character of Alfred Borden over Robert Angier, he's a far more interesting character at the end of it.
Obviously, haven't seen Public Enemies, but it's the story of the hunt for John Dillinger and, in part, the formation of the FBI. It's never going to be the latter that's more compelling, and Bale's character is suited to being second draw to Depp's Dillinger. Saying that, he's in a Michael Mann film alongside Depp and Cotillard... I don't see how thats losing any steam.