Other things working on server are AD, DHCP, DNS, file services, web services
This is not a criticism. I'm only commenting for the benefit of you and your company.
It is definitely NOT a best practice to have the other products you mention ("AD, DHCP, DNS, file services, web services") executing on the same server as your SQL Server.
I know that sometimes, for reasons of economy, companies must do this but if you have the option to move SQL Server or the other products to different servers, I would do so. Doing so is most likely to give you the best results for all of the products and especially SQL Server.