The lack of a proper "fogging" effect is almost certainly due to a lack of post processing, can you ensure the make sure you don't have the -no_post_proc flag on (this is a known issue, and it appears the push is to deprecate support for no post proc entirely). Regarding the poof bitmaps themselves, if that's what you were referring to, the MVP poofs have always been very wispy and subtle; the latter picture is largely what I expect to see, and more or less what you should've gotten before, although it doesn't look like there's any at all in your first picture...
I'd be interested to see a direct comparison before and after the change for you, I wasn't able to replicate anything unusual on my end.