Struggled with this mechanic during a pug raid. I was using the "Raid Notifier" addon, if it matters. We were attempting +3 on normal, again ... if it matters.
Researched it as best I could, but still confused.
As I understand it ...
1) Periodically, two players will be targeted with "Voltaic Overload".
2) The two players will receive advance warning (a message on screen).
3) This will be followed by a second or two's "grace period", during which the player can (ideally, but optionally) select the bar they DON'T want to be on for the next 10 seconds.
4) Multiple super-fast swapping in that grace period is fine, if the player (let's call him "me") is a bit of a spaz!
5) At the end of the grace period, the player receives a blue, vertical, sky-high aura over their head AND simultaneously finds themselves standing in a humongous light-blue ground-AoE'ish circle.
6) Upon seeing the blue circle/aura, and as soon as possible after that, the player MUST swap bars ONCE ... and from that point, can NOT change bars again until the 10 second timer runs out.
7) The instant the player swaps to their "10s bar", the blue circle/aura disappears.
8) While holding that bar during the 10s phase, the player can do what they want (move; attack; shield; heal; etc)
9) On "Raid Notifer" a timer counts down the 10s, which is helpful (not sure what happens elsewise).
Failure to do #6 (the first part: aka "the swap") causes death, destruction, and drama.
Failure to do #6 (the second part; ie: subsequently swapping before the timer expires) ... causes death, destruction, and drama.
Is this correct? Any additional guidance you can provide would be very much appreciated.