Hearthpwn

I want to log on and try out new decks easily, so my goal when I buy a pack is to collect the most unique cards.

edit: for example, I don't have any primordial glyphs and that hamstrings me when I see a new deck on the "hot list" that uses them.  I'd like to PREVENT this through buying packs so that I have to craft the least number of cards possible.

I am trying to figure out which card set is the best set to buy a pack for from a statistical point of view.  This assumes you are not gunning for a particular card, but want to be best prepared for the next HOT deck.

I think that the only rule we have to go on is that we are guaranteed to get a full set of epics (purples) before we get dupes of those.  I am not sure how the "mercy" rule works.

Therefore, my thinking is this: forget about getting legendaries for now and try to complete your epic and below collection.

First priority: classic packs, as those cards are much less likely to get retired.  Unless you are only missing one or two epics that you know are pretty useless.

Second priority: which sets are going to go out of circulation next.  

Third priority: which set do you have the least epics in.

All of this assumes you are not shooting for a particular epic, which seems pretty frustrating with the packs full of duplicates I keep getting in witchwood...

Given these goals, I'm having a bit of a time using the Hearthpwn tools to automatically count my missing epics per set.  Using the "my collection" item under my user name, the tool provided doesn't seem to allow one to search by rarity.