https://support.safe.com/hc/en-us/articles/25407794017933-Performance-Tuning-FME

In here there is a section on performance profiling: 
 

Additional Performance Tuning Tips

In FME Workbench, you can run a profile of your FME Workspace to obtain a detailed log of how much time is spent in each underlying factory or function. Use Tools -> Edit Header to add the directive: FME_PROFILE_RESULT_CSV i.e:

FME_PROFILE_RESULT_CSV C:\TEMP\profile.csv

Notes:

• The profile directive is not supported on FME Flow
• Don't forget to remove the profile directive for your production workspace since profiling also has an impact on performance!

It's sometimes worth using a Performance Monitoring tool (such as PerfMon) to log the CPU and memory usage of a process.

It’s not quite a breakdown per transformer I don’t think, however, it does give you an indicator on which factories are using the time.

You’re right in that it’s a bit of tedious process, and even going through the log doesn’t always give you a good insight into where the bottle necks are but it is really important still. 

In general going through this article series is great and will give you some excellent insights in how fme works

 

Just remember to remove the FME_PROFILE_RESULT_CSV setting before publishing the workspace to production, as it can introduce quite a lot of overhead on each execution.

Also, make sure you’re only working on local files. Directly working on large files on a network drive can be catastrophic for performance.

100% - at least this is nicely hinted at in the log file (CPU time vs Total Time)

Thanks ​@virtualcitymatt and ​@david_r ,
That’s pretty much exactly what I’m after. I’ll be able to do this to find the worst bottle necks