Jrrr...seriously? Have you ever actually played 5th gen? Even if you haven't, i'm sure you can figure out what priority taunt, encore, and stun spore means. Here's a hint: it means that while erefuun is alive, you aren't walling, stalling, setting up or sweeping, and most of your team will be paralyzed (even grounds) in the process. How you came up with such negative theorymon is beyond me.
It's far from broken...it has a few hard counters (starmie, scizor) but people are starting to run switcheroo to deal with some of them.
Jaroda, Borutosu doesn't have the movepool to abuse Mischievous Heart with. It does get taunt which is great on it, but T-wave is blocked by grounds (unlike stun spore), it doesn't learn switcheroo or encore, and erefuun learns u-turn anyway.