I expect if you came down on a Tiger, as in straight down say with a Jug, and fired all 10 Holy Moses's at once it would make a big enough bang in the weak part of el Tigres armor to make it blow. Ive never tried it. Frankly you just dont see Tigers all that much.
I know the Yank 5" rocket was made with both HE and AP warheads. It was a very fast rocket and I heard it was pretty impressive when a salvo hit an enemy. The warhead was about 50lbs of HE and 10 of them slamming into a tank would really rattle it I'd say.
The Russian rockets are so useless its not even worth the drag price of loading them. Which is also pretty correct modeling too. In real life they werent much of an asset.
In the game, personally, I find the Brit 3.5" rockets the most accurate.