Carl makes some good points. But building on the home performance, try to reproduce at the office. The fact you state it is much better when you are the only one using it could mean something. One user, maybe on wired, it is fine. When you are using it alone, then start another user on a different computer. Does it slow down. This could still mean it is on the other end, but it could also mean it is on your end.
Work yourself with a different computer (when alone).
Humans tend to look at what seems obvious. AC Cloud. Possibly. But, still consider there may be a networking problem on your side. Again, though, another user shouldn't slow it down that much given the work is being done on their side.
Ask AC if over the weekend, they will set AC up with just a test user on a different server in the cloud. See how it works then. If it still has issues, it imay be their side. If blazing speed with four connections then likely their side.
When your IT looks at the network performance, it should be done when the problem is occurring as well as when not.
