Using Resource Governor and allocate more memory to satisfy high Memory Grant request by queries?
This is the opposite of what you should do.

When you have queries waiting on RESOURCE_SEMAPHORE, they're waiting for other queries to finish running, and give up their memory. The queries that are waiting aren't even running.

Letting all queries use more memory will only make the problem worse. You'd wanna configure resource governor to make queries ask for smaller grants. This could also cause problems, though, because any spills to disk would get worse.