I think Mark is right.
I also only see from sysmon quite high "Spinlock Contention" on default data cache.
First you shoud eliminate this problem and then check if this help.
Very interesting post about spinlock is:
This is more about 15.7 and 16 but aslo for you could help.
I think you could start with:
- increase default data cache to 64 partitions
- create extra cache for some "hot" objects
- create extra cache for system tables
-create extra cache for log