The performance on the Data Services side will depend on a number of factors when passing in IDocs to the target ERP / CRM system. The factors below can all play a part in slow performance.
Network speed between DS and SAP target
Depth and compexity of the NRDM structure (in the case of BP can be complex)
Processing capabilities of the DS box, i.e. number of processors, memory, etc.
What kind of processing is being triggered on the SAP side.
In the case of 1 and 3 there is not much I can advise on other than the better the network round trip and better the hardware clearly improvements can be made.
With regard to point 2 ensure that you do not have redundent schemas within you BP model (i.e. all fields are null) and ensure that you have specified all of the required where clauses and from clauses correctly to ensure you are not creating duplication at the lower level schemas. You can test this by dropping in a template XML file as an output to the data flow also to look at the structure of the output IDoc.
With regard to point 4 you need to look at whether you are triggering the IDocs immediately or holding for background processing. If the former is true them in WE20 switch the IDoc processing to background and then use program RBDAPP01 to allow you to setup parallel processing of the IDocs on the SAP side making use of all application servers available.