So, I thought I would crunch a few numbers after this rule was introduced. The following assumes you are going after T4 or below models with 1 wound. I mean if you're going to come up under a Nemesis Dreadknight you're asking for trouble.
Five models, no invuln save: odds of Deep Strike mishap is: 13 %
Ten models, no invuln save: odds of Deep Strike mishap is: 25 %
Five models, each with a 5+ invuln save: odds of Deep Strike mishap is: 92 %
Therefore, if you go for the nice squishy option with no invuln save then your fairly safe. Also consider this:
Roll 4, 5, or 6 on the DSM table then it's a BONUS. You don't get shot at and you get an extra Terror from the Deep.
Roll 2 or 3, then if your opponent places you far away in the corner. Then great you aren't going to get shot, just burrow next turn. If they place directly in front of some big guns, then you were probably going to get shot anyway by them as the model is so large.
Roll a 1 and it's
However, overall you got three times the opportunity of rolling a 4, 5, 6 than a 1 on the DSM table. And it's possibly worth trying to deliberately DSM on say turn 4 or 5 to try to get a 4, 5, 6 on the DSM table to get one more TFTD which you otherwise wouldn't have and if you rol a 1, then you're not much worse off anyway.
Overall I think that though on first glance they nerfed the Mawloc ,I think they have actually made it better - it's more of a risk, but it can do more damage. Just go for easy targets the first turn, and leave the tougher ones for later in the game.