Gefion's poor return on displacement

Was Gefion's 4,200-ton displacement justified by her capability?

No; a Pearl-class cruiser achieved broadly similar capability on roughly 2,500 tons.

The comparison turns displacement into a direct measure of design efficiency. Gefion's capability would look plausible on a ship of roughly 2,400 tons. Instead, she displaced about 4,200 tons. A contemporary Pearl-class cruiser delivered broadly comparable capability on about 2,500 tons, making Gefion's extra size difficult to justify.