Right now at the quietest part of the day with probably half the company having taken the day off our busiest SQL Server database is fluctuating between 250 batch requests per second and 800 with regular (every few seconds) spikes up to 2500+. about 800 over a 30 second average.

I don't have any other metrics to hand but when the business are using the application in anger I'd expect to be averaging about 1500 to 2000/s

we also get peaks of activity during import phases which occur throughout the day - don't have any metrics on that unfortunately.

CPU is between 0 and 1%, DB I/O is less than 0.1MB/s

I'd think that 1000 transactions per second is actually quite low usage on a system with the number of users we have. I'd think our server could probably handle upward of 16000 tps maybe even 20k at a push.