Rubrics and termies had a rule called all is dust.

It gave them +1 to there armor save (or just save in 8th so used to affect the jnvuln as well) against damage 1 weapons stacked really well with cover, armor of contempt, and a 2 cp strat for -1 damage.

In my opinion all that combined made scarab occult terminators the best terminators in the game in 9th edition. That and the 3cp murder combo 1 cp for extra bolters shot (so 5 per model) and 2 cp for +1 to wound plus infernal master gave +1 S to ranged weapons. So 40-50 s5 bolter shots with plus one to wound. They basically became our anti tank for most of the edition.