I just received a new Shimano Deore rear derailleur, which has large gobs of lubricant in two locations (one clearly visible in photo). This seems excessive.
Do I leave it, or are they expecting you to wipe the excess away before installing?
I'd wipe it off a bit--it won't serve any purpose as it is, apart from collecting dirt.
All of that goo is very typical of drivetrain components that are fresh from the factory. The factory uses a particularly thick lubricant to protect the parts until they're purchased or installed (lest they sit on a shelf and risk being exposed to moisture).
Basically, the factory is expecting whoever installs said drivetrain components to identify any excessive grease (some of it is there for good cause, such as protecting the inner spring from the elements), wipe it down, and re-lubricate with something lighter!