I too have dreadful reject rates - between 8 and 15%. Turning off submission of stales just causes my stale rates to spike up.

I've seen this with other multipools, but they were able to adjust something which got the rejects down to a normal (1-3%) level. There's a lot of money being left on the table as it stands with these rejects

I have a few 'pending deposits' from a couple of days ago in the Auto-Exchange Transactions log - is this something to worry about?

If it's possible to sort the rejects out and the offline notification system turned on, I'll certainly be adding more hashes to the pool.