Yay, I've won 8 flying weapons from these "farms" instead of actual rares. Not to mention how much less score and electrum I got because of not getting masterity.
Biting farms are stupid. Beginners might play top 50 for the rares, but after some time they'll have tons of them.
The real purpose of farms is an acceptable way of electrum (and to a lesser extent score) farming, other than the false gods.
Biting farms are unfit for that, while also reducing the chance of winning a rare a lot...
Besides, to farm to 50 you need a very strong deck, so it's not like you get the rares for free. You'd still need to be able to have a decent win rate against the remaining top 50 decks, if you don't want to lose lots of electrum and score.
I'll never, ever make a biting farm...if I want to give people a challenge, I'll load my strongest pvp deck, and if I want a farm I'll make one optimized for farming, and having only the cards least commonly seen in farms or having the highest electrum value. These biting ones are useless for both purposes, they don't provide a real challenge (except for a very few, they at annoying at most), but they are considerable worse for farming as well.