Dihydrocodeine can have an upper limit as side effects build. Oxycodone is more efficacious and a stronger agonist with far less side effects vs any of the codeines at equianalgesic doses IMO. The histamine release from DihydroC would probably put the ceiling at about 450-500mg if one's tolerance would allow them to take that in the first place. Things like itching, hives or more serious like a swollen shut throat are the main dangers of histamine release, antihistamines can help, but not always.
On the downside Oxycodone is more addictive for most so there is a trade off. If you are able to rotate then that would be a decent compromise but I wouldn't avoid the DHC because of liver worries unless it has APAP-paracetamol in it.