I wouldn't necessarily say acceptable, but common, and often the only way they can do it. You have to remember that it takes 4 hours to get a whole section of dressage completed, but only an hour and 20mins for them all to go XC. If they run, say, a Nov followed by a PN on the same day they like to get the PN dressage out of the way so that once the fences have been changed from Nov to PN everyone's done dressage and ready to jump.
Annoying, frustrating (especially for me last weekend!) and useless if you've got a horse that switches off, but unfortunately logistically the only way that they can run 300 horses in a day. It's either that or ballot half the entries......
I have a 4 hour wait at my ODE on Monday (you don't happen to be going to Catton Park?); the same as last year.
The problem is they do all the dressage in the morning (cheaper to get all the dressage judges done and dusted in the morning, so they told us!), then the novice jumping, intermediate jumping and finally open jumping. So if you are in the open like me, you have to wait till 6pm to showjump
Haven't experienced that problem at affiliated though- this is an unaffiliated event I am going to.