I work as a Splunk integrator and here's what I often see:
1. Customer installs Splunk with a qualified Splunk or third-party architect team. The deployment works well.
2. Customer adds infrastructure to the deployment. Splunk slows down. License costs go up.
3. Customer chooses between outside help or DIY. DIY rarely works.
4. Customer now needs outside help. Now Splunk is very slow and expensive, and now it will cost a lot to tune it.
Splunk, the company, is in a tough spot for several reasons: rotating c-level cast, unpopular changes to license model, bad acquisitions. The product is still best in class but tough to keep optimized.