If you want to make a large-scale study of this, here's my suggestion:
Find 5 people who have a given tier of Snatch. Find 5 people who don't have Snatch. Have both groups spam the Expert event fight for the rest of the week, counting the number of boss kills and the number of Hearts of Apocalypse they get. Counting stacks of Snatch is too tedious (and there's 5 mobs to keep track of each with potentially different drop rates...); but we're only looking for an effect anyway so we don't need to.
Bring me the data from this and I'll run the stats on it (I'm a computational biologist and I've done these sorts of analyses for my PhD project). If you want me to also do a Chi-squared test (which can be a bit more sensitive than a t-test sometimes), I'll also need the number of runs where no Heart of Apocalypse dropped.