I don't think it's ever considered bad. Its just some of the rares are attainable in the elite instances and plot instances. Its safer to get a rare in tendo treasure beside...everyone just wants to get Hashirama and Tendo pain...Tendo just have more to offer, but seal treasure is not bad. It has the legendary Chiyo and Konan.

actually alot of the ninjas on seal treasure is attainable in game for free. It's better to draw in tendo treasure for that reason. Pain characters are amazing anyways.

farrrrr in the future, it will show up in the redemption shop

eh...Ao is a pretty good ninja...if you're a water main.

http://naruto.wikia.com/wiki/Ao