can multiple hubs plugged into a switch slow it down?

I started at a new job 3 months ago for windows/vmware esxi administration. I'm pretty weak with networking. The datacenter has a 10gb link to another building on the same property. latency is high and speed is low. When users log in, they don't get their group policies or drive mappings. I've changed the GP to "wait for network" before logging in but it hasn't helped.

I've noticed that the dell powerconnect switch in that building has no less than 4 hubs plugged in, because the maintenance guy did not want to run multiple network cables. I'm wondering if this could be impacting the network config and causing the slowness. Any ideas please? Thanks!