Heya and welcome back!
Just two days ago while I was reading my rulebook in the friendly neighbourhood LGS, I stumbled upon another way in which units could get down from ruins without needing to roll for difficult terrain, albeit a much more dangerous route. The text that are bolded will come into play later
As stated in page 99 of the BRB;
A unit that is not falling back and descending through a building can always elect to Leap Down to a lower level, rather than making a Difficult Terrain Test. However, all descending models in the unit must take an Impact test (see page 95).
And what is an Impact test? For this we refer to page 95 of the BRB;
To resolve this, choose one model from the battlements and place it anywhere wholly within 3" of the base of the building that is at least 1" away from enemy models, and not in Impassable or lethal terrain. That model must then take an impact test. This is exactly like a Dangerous Terrain test, with a -1 modifier for every full 3" the model has dropped. Unlike ordinary Dangerous Terrain test, armour saves cannot be taken against Impact test. Jump INfantry and Jetpack models must still take impact test but they ignore any modifiers from falling 3 or more inches
If the model is slain, choose another model and try again. If the model survives, resolve the same sequence for all the other models in the unit, taking care to remain in unit coherency. Any models that cannot be placed for whatever reason, are removed as casualties with no saves of any kind allowed.
It was then that I realized something kinda evil too, as I remembered the wording of Lash of Submission from the FAQ but just in case I went ahead and talked about the terrain test in itself first, and allow one of the LGS staff who is knowledgeable about 40k to somehow spark the idea. And soon enough he told me about the thought that I have out loud; you can definitely lash people from ruins down to their deaths.
This in itself makes the Lash of Submission quite a deadly counter to all those happy campers up on the ruins as they will be forced by the player who move the unit on whether they will walk down or jump, and obviously with such a deadly effect, the moving player would elect for the unit to jump down. Any type of test that could kill people off is not pretty, and with such modifiers to the test you could kill quite a few people off too. And this is before the pain of the enemy shooting comes into being and other nonsense.
Nasty, nasty, nasty........