Hmm. Well, it's a puzzle, isn't it? I tried to work out a formula based on estimated rate of weight and fire, and I replayed the encounter off Norway between the Renown (6 x 15") and the Scharnhorst and Gneisenau (combined total of 18 x 11"). The Renown got massacred under an absolute avalanche of 11" shells, and was sunk in short order.

But in the real incident the Renown scored a single long range hit on one of the German ships, and they disengaged at high speed.

If what you say about the firepower of heavy cruisers is correct, the Germans were wise to have the Prinz Eugen stay in the battle and assist the Bismark in the fight with Hood and Prince of Wales. In fact, the Eugen may have been the ship which really won that battle and blew up the Hood, but that remains uncertain.