As you can see, I killed amongst other bosses ji-kun Wednesday, I killed her again yesterday. My lockouts reset when I changed, as did the rest of my guilds. I had a friend transfer from another server, his lockouts reset twice so far (they reset when he went from our home realm to another realm, and then from that realm to the realm we're on now.)
We went from Alliance on one realm to Horde on another realm in the same battlegroup.
It works randomly. As recently as 5.1 I transferred and ALL of my lockouts reset (Valor cap/Conq cap/LFR/Normal-Heroic Raid Lockout). I've also transferred after that and seen it not work. So people who are giving a definitive yes or no (especially those being rude about it) have no idea what they're talking about.
Blizzard is good at creating some RANDOM effects.
It is not a bug.
$25 for a chance to reset lockout.
everything but HEROIC lockouts will reset
A server and faction change will reset the raid lockout numbers, but not the bosses already completed for the current week. If you already killed a particular boss, it will still not be loot eligible for you until the next weekly reset.
when all else fails, read the STICKIES.
Faction/server changed a character last week and nothing reset. I moved it to another server (was picking up some gold from my horde chars) once the faction change went through and again nothing reset.
Moved another character later on that same day doing a realm and faction change at the same time (there is a tickable option when selecting server change) and again nothing reset.
To note; I changed battlegroups in the process.
So to confirm, no nothing will reset no matter how you do it. Yes it did used to reset in cata but was stopped as I believe the guild Exorsus used this way of resetting raid lockouts to get a 'glory of the whatever' achievement world first and blizz did not want to promote this kind of gameplay, one where competing world first raiders would feel compelled to faction/server change to win.
If anyone remembers Why stars got banned for a week in the 1st week of FL. nothing about the saves has changed yet. Even envy did the same thing in the 1st week of DS and T15.