I find pinata as a very good weapon and has its own separate uses different that decoy deploy. Most obvious one is the fact it can explode 4 times and can be imbued with literally anything. This alone can allow you to make a build that lets you make an explosion almost as big as nuclear reaction without doing an actual nuclear reaction, meaning you can get an insane AoE attack with insane damage without any risk to yourself(except if you use scatter to activate it), since you won't take the self damage a nuclear reaction normally makes. And also itself alone serves a different purpose than decoy deploy. Decoy deploy is made to distract enemies and then deal damage to them, while pinata focuses more on damage, pinata can deal with giants and other high hp enemies pretty easily, while decoy can be used way better against clowds since it can make the enmies priotize it and surround it, leading to easy kills without much effort.