I'd prefer Vault/Acrobatics over Entangling. And Archery over Tacticals, but Tactic over Sharpshooter. Tort ground on Caltrops too.
That's my build. I have quite a high crit chance so I don't need Sharpshooter though. I'm only at 100k~ dps with Sharpshooter but it seems to do the job for me. Haven't tried it solo but with 1-2 others and haven't found it *too* hard.
Do you have any specific strategies to clear it? It seems like most people start by having a DH/Wiz clearing the trash mobs and leaving the pony's and any unique packs. Then getting 5 stacks of NV from the Festering Woods/Cemetery/Fields of Misery with friends then all going back to Whimsy. Pull all the ponies into the tree glitch and kite them down. Kill any unique packs if possible but if not just leave them. Is that what you guys have been doing or do you just clear it as if it's a normal dungeon?
I always start whimsy with 5 nv stacks. Before the clear, pop over to the cemetery and clear the 3 tombs. Takes but a few minutes and 85% of the time this will give you your 5 stacks. If i can't get 5 from the cemetery, ill pop over to the cathedral or halls of anguish and hunt down that last elite.
So basically what u have + KT's suggestions. The only difference is I use bat companion over entangling shot. I clear it solo without any problems. The only exception is when there's an invulnerable pack... I either restart the game or I park them in a corner. Reflect dmg can be a bit annoying too, but after a bit of practise I've been able to start managing them.