I really think Espeon is Broken, what!? you'll say, but it's not broken in the regular single-pokemon-which-destroys-a-full-team kind of way, it's how it makes BP teams, really dangerous, I think is really pushing them over the edge, any BP team has to relly on Taunt to avoid being roared/taunted themselves, but espeon has BP (which means he doesn't break the chain) and Magic Bounce which makes him unable to phaze outside of D-tail (which sub blocks) and haze, he can come when you want to yawn/taunt/leech seed/t-spikes/use hazzards/etc..., just pair him with Mr. Mime to avoid Perish song (which almost nobody uses) and you can't break the chain in a reliable way, not only that, he is the perfect receiver since a STABed Stored Power is gonna OHKO everything after a few passes, and HP fighting or signal beam are enough to kill dark types
I made a team which only dierences was Milotic (scald, rest, sleep talk, and D-tail/Haze) the D-tail one lost to every BP team since even if i predicted correctly and scalded a sub, they could ressist it thaks to SpD boosts, or they spored me, then i used the haze one, and completely destroyed every BP team but one, that to me tells me how good can this stategy be thanks to espeon since he doesn't really care about phazing or status and he has always a sub so he doesn't have to worry about being KOed (and after a few boost nothing bar a crit whil take him down before being OHKOes by Stored Power)
And no Xatu is not broken since even if they share the same ability, similar typing and Stored Power, he doesn't have BP, not legally (which is really a huge difference), and he breaks the chain whenever he is passed the boosts, so you can only swich to him once, Espeon is another part of the chain, and he can continue to pass the boosts