We're seeing same poor performance here. Effectively we, too, had to downgrade to 2.2 version as 2.3 was unusably slow (it got completely stuck - no more response from Web UI within 15 minutes).
Environment: Oracle JDK8 (_66) 64bit, Jenkins 2.8, AD Plugin 1.47 (no Domain name or other advanced settings entered, I guess that means we're using ADSI), Windows Server 2008R2 64 bit (Domain Member), Hardware is a VM with 24 GB RAM (of which 9 GB are dedicated to Java mem pool), 6 CPU cores and using an SSD storage cluster.
Most significant difference to initial report: We're NOT using AD groups at all. Roles are assigned only to users.
We currently have 37 roles (31 regex-based project roles, 6 global roles) which are assigned to roughly 100 users.
The Jenkins instance contains ~50000 jobs (organized in folders).