Definitely ends badly for Villa managers. The managers we've had in my time as a Villa fan are Big Ron, Brian Little, John Gregory, Graham Taylors 2nd time, DOL, MON, Houllier, Mcleish, Lambert, Sherwood, Garde, Di Matteo and Bruce.
None of them have done anything of note after leaving Villa. Bruce would be toiling back in the championship right now with Sheffield Wednesday if it weren't for the fact that he's a Newcastle fan and bring used to draw the flack for Ashley. DOL, Mcleish, Di Matteo, Taylor, Sherwood either retired or just gave up. MON had a crap spell at Sunderland then a mediocre time with the Irish national side. Garde is in the MLS. Little never managed at the top level again. Gregory ended up managing in Israel and India. Lambert is currently mid table in league 1. Big Ron did manage a few premier league teams after leaving but always in relegation scraps.
Maybe we're cursed or maybe once you've been the boss at the best club in the world it's inevitable you're only going down.