I’m surprised that you only have 120 links in a graph with 2252 nodes. That should layout pretty quickly.
Are you using version 2.3 of the GoJS library? We recommend that you set LayeredDigraphLayout.alignOption, usually to go.LayeredDigraphLayout.AlignAll. That should help with the layout time.
I was asking for typical numbers within the Groups.
2000 and 18000 are only for top-level Nodes and Links? Or are those the totals for the whole diagram?
How long do initial loading and group expansion take?
It might be helpful if you provided a screenshot so we can see how the graph is structured with so many links.