I haven't really had much success using U-turn on Whimsicott. Unless you actually put a lot of speed EV's to outspeed most of the metagame (particularly max 328 speed dragons or 333 for garchomp), you're going to take enough damage for it to matter on effecting your leech seed stall and we all know how often dragons are used. I'm probably doing it wrong, but do people really use U-turn without investing in speed? It's amazing at scouting, but due to the fact that teams are see-able before matches, it doesn't matter nearly as much.
I've found Taunt and Encore a must have on the stall set despite it being a little predictable (Reuniclus will hit you hard still if you let it continue to calm mind after encore and that struggle damage can be really good, although you're going to need a really strong revenge killer after before it can recover).
I've found Taunt and Encore a must have on the stall set despite it being a little predictable (Reuniclus will hit you hard still if you let it continue to calm mind after encore and that struggle damage can be really good, although you're going to need a really strong revenge killer after before it can recover).