@KyleGTerminator
When the Zany Zombopolis Pack first appeared in the shop, for the first month or two maybe, it seemed like that Pack couldn't shove Legendary pieces into my hands fast enough but speaking with other players since then it seems that I was either phenomenally lucky with the drop rate or it's been adjusted at some point over the months since I completed my roster of characters.
When Frontline Fighters debuted It dropped all the character pieces for every new character except for Commando Corn within me spending a few hundred thousand of my horded PvZ coins but then refused to give me any piece of Commando Corn until I had spent close to another 5 million PvZ coins.
I'm at the point now that I simply make certain that I have several million PvZ coins stashed away both for Rux's visits and also against the possibility of new variants which need to be dropped from new Sticker Packs.