Here's my only complaint: Farms that put way too much variety in their decks. I love fighting biting farms - the ones with, say, 5 animates, 6 of a rare weapon, and a bunch of towers with the same element of the weapon. If I beat it, I get a nice reward - a decent chance to get the rare weapon. However, there are, say, Morning Glory farms that have, for example, 6 Morning Glories, 4 Miracles, 3 Leaf Dragons, 3 Emerald Dragons, 4 Stone Skins, 3 Elite Otyughs, etc. - I can still beat it, but the chances of winning the Morning Glory or even Miracle are skewed to hell and back - it ends up being like trying to win an upped card from a level 5.
Of course, this is just my personal opinion. T50 does not need to listen to it - I'm grateful that there are farms out there where I can complete my rare collection.