Its a bug. If anyone goes back on the minefield after the turrets are turned off they'll respawn. This can be fixed as already stated by waiting for the player who is up top to catch up to the raid before hitting the panel. Assuming you arent close to enrage. Pretty sure if they do respawn the enrage timer is either gone or reset. Either way they dont hit very hard and shouldnt cause you to wipe at that point unless your raid is under geared.
Uhhhh nope. Ran this wednesday evening, one shot it, no turret respawn, and I hit the button the INSTANT we crossed the field. Tower tank was WAY out. (Hell, last week he hit a mine on the way in somehow. that was funny. We 7 man'd the boss. )