We have benchmark to support WebLogic domains that have 40+ ManagedServers and 50+ data sources. And all our page load is between 1-3 seconds for this domain and WLSDM perormed really well.
For your case; the most struggling thing is going to be completing WLSDM wizard; if you are enough patient wait for every step in the wizard process.
But, please first of all try it in your non-production environment.
We are ready to solve your cases and performance bottlenecks.
How many wlsdm_agent are you planning to install on managed servers?
WLSDM Community Support Team