German 12"/50 had a max possible penetration of 13.6 inches of armor (dead perpendicular to the plate) at 10,000M. The RN
QE & Revenge class ships had 13" armor belts. Most of the rest of the RN heavies ran 12" belts. Except for a perfect hit, obtained in rolling seas, by ships making 18-20 knots the British Super Dreads were invulnerable. Deck armor is not an issue since none of the ships, on either side, could elevate sufficiently to make plunging fire possible. Conversely the 15"/42 on the
QE & Revenge had sufficient over penetration to defeat the belt armor on every ship the HSF brought into action, and the 13.5"/45 was marginally more capable of defeating the HSF heavies belt, although far from certain to be successful.
There is a tendency to forget the remarkable protection of the RN battleships because their BC were so remarkably fragile (
Invincible's belt was only 6" with
Lion & Tiger class running 9", by comparison the
Derfflingers carried belts of up to 11.2", nearly equal to the HSF heavies). This is very much an error. The BC should never have been used in the battle line, that was not their role, and they were ill-suited for that sort of slugging. They were designed to kill armored/protected cruisers and act as a force that could find, fix and defeat opposition scouting forces. Results demonstrated very nicely that the strategy was fatally flawed, in no small part due to officers seeing guns as big as on a BB and attempting to use them as such. The same sort of error cost the USN two CLAA off Guadalcanal when they were used in the role of cruiser, something that they were utterly ill-suited to perform.
There is also the not insignificant matter of light forces, here the GF had such an overwhelming advantage (better than 2-1 in CL and the GF had a 15% numerical advantage, as well as a qualitative advantage, in DD).
Lastly, there is the reality that history has demonstrated that actually sinking a battleship with gunfire is nearly impossible. They can be battered, turned into scrap, and left unable to defend themselves in any meaningful manner (as demonstrated in WW II on several occasions), but actually putting one on the bottom is another story. They can be killed, but the big guns won't be enough. You need to pound them flat and then kill them with torpedoes. Given all the factors noted above, there is no reasonable manner to get the entire GF into the condition necessary for that sort of
coup de gras.
Wiping out the Royal Navy heavies is simply not going to happen without Skippy the ASB putting in an appearance.