I also don't blame not bunting as the problem.
Beltran was surely upset, but I can't think it really matters all that much how he gets out and it's not like he made a mental mistake. He got beat on a good pitch. It'll probably happen dozens of more times in his career (or more)as I would think it has already happened that often already. Anyway, I think he'll sleep fine once he puts the whole series behind him.
As to the Wagner, I would rather their best pitcher, the guy they hired to do exctly what he wasn't given a chance to do, be the guy facing that order. I understand that Randolph was lookng to get an extra inning from Heilman figuring it would be extra innings. And I can't entirely fault that reasoning. So even though I would have put Wagner in, I won't really hold it against him.