I have a love-hate relationship with mechanics that targets one player that, if not handled right, very easily wipes the raid. Such as defile from LK or the bomb thing that knocked people up in TK.
Mostly it's because it always seems to target the people that has the toughest time to grasp the mechanic out of all the players in the raid. It's stupid when it gets to the point that you have the kill as long as a few select players does not get targeted by it. But it always feels awesome when those bosses die after you've wiped countless times to said players getting targeted.
Amber Shaper's transformation also counts into this. Mostly since it's a vehicle thing that only targets one player at a time. Unlike Flame Leviathan in Ulduar where everyone had vehicles.