I agree that $400 would be much too much for a pavillon room. I paid €169 last time I staid in the Pavillon building when the hotel still was a Westin, this price was ok for that room, more is not ok. The Palace building deluxe rooms are significantly larger with chimney, high ceilings and a big and comfortable bathroom. As Diamond you should have been complimentary upgraded to a Palace room, even on a reward stay!
The brasserie La Veranda is a good alternative to the 2* gourmet restaurant and less expensive, food from the same kitchen! Beverages of course same prices.