I was consulting one of Dell's customers a few years ago which had trouble with SQL Server Performance on ESX Hosts.
Took me 3 days to capture some metrics to be able to determine that the SQL Server VM wasn't passing any Disk Queue Depth to the SAN Array.
I wrote a short summary for the customer how the issue looks like. Same day I got an invite for a conf call.
During that call I explained in detail what was happening and that from a SQL Server perspective I'm unable to fix this, eventually some drivers or ESX settings change might solve their issue.
When I was done telling my side of the story, the CIO got furious, really furious.
He said "How can it be that you couldn't tell me earlier what's wrong? We're dealing with this for a year(!) now, have been checking hardware and ESX for ages but it takes the SQL guy to take a look at the OS level?"
It wasn't pointed towards me but I still felt bad for them so I replied "I'm sorry, you didn't reach out for me earlier …"