As I read your comment, I came up with an idea.
Atium, you see, has both temporal aspects and mental aspects. You can see into the future, and your brain can process the information more effectively (I would also assume that it gives you a bit more Ruin, compared with the body's natural Ruin/Preservation, just like lerasium gives you a better link to Preservation. However, unlike Preservation which gives you a clear magical effect, this Ruin-side effect may be more related to the violence one inflicts with atium, as Sazed notes in the epigraphs of MB3).
As alloyed-atium grants expanded mental and temporal aspects, and there are two clear components in atium's Allomantic effect, I think that the converse is true for lerasium. Its Allomantic power is physical and enhancement in nature, most likely.
That's really interesting, actually. Whereas normal metals have a pair in the same quadrant, like gold and electrum, atium and lerasium are on opposite halves of the metal wheel.
So, if atium grants invincibility through mental/temporal means, which in effect it does (brings a whole new meaning to god metal, yes?), lerasium may grant invincibility via physical/enhancement methods. That seems really plausible to me.
If this is true, there better be a frickin' lerasium vs. atium burning battle in a later Mistborn trilogy, or I will be extremely upset. That would be all kinds of awesome.