It's true that Hipper's German battlecruisers went on quicks runs to shell some east coast towns in the UK...but not because there was any military value really in doing that. They did it in order to lure forth a British battlecruiser squadron. It was hoped that they could lure a relatively small part of the larger British fleet within range of the entire German fleet. The German battleships were waiting farther to the East to pounce on any isolated British force. The idea was that Beatty's battlecruisers would pursue the smaller German battlecruiser force within range of the entire German battleship line which would then overwhelm Beatty's ships and destroy them.

If this could be done, then the Germans might get closer to achieving parity in naval strength with the UK. If that could be done, then the Germans might be able to break the blockade or possibly even defeat the Royal Navy decisively in some future battle.

This was what the Germans were attempting at Jutland. It failed because Jellicoe was following up closely behind Beatty with the main British fleet...so instead of the Germans trapping the British and outnumbering them, the reverse happened. It could have resulted in the utter destruction of the German fleet, but they managed, with considerable difficulty, to make their escape during the night.

The Germans had very tough ships, including Hipper's superb battlecruisers, but they simply didn't have enough of them to take on the entire British fleet.

As for the British, their battlecruisers were extremely thin-skinned and vulnerable, but their battleships proved to be tough customers. The Queen Elizabeth class in particular (including the famous Warspite) were probably the finest fighting ships of their day, mounting 15" guns, and they were still around to give excellent service in WWII.