Any groups besides mantispids that characteristically/exclusively go after spider egg sacs?

other egg sac predators/parasites

There are a number of hymenoptera that prey on the eggs inside spider egg sacs. The question seemed vague to me "go after spider egg sacs" maybe you only mean that take over the entire clutch? Scelionidae commonly parasitize eggs within egg sacs and emerge without attacking other eggs, so there are occasions where both some of the spiderlings and some of the wasps emerge from the same spider egg case. I am fairly confident (but not certain) that there are others too.

… Richard Bradley, 3 November, 2016 - 8:50am

Some flies

… John R. Maxwell, 2 October, 2016 - 2:18pm

egg predators

I can send you a PDF of this paper or you could go to the AAS website and read it. We included references to other papers on egg predators.

Predators and parasitoids of egg sacs of the widow spiders, Latrodectus geometricus and Latrodectus
hesperus (Araneae: Theridiidae) in southern California
Richard S. Vetter1, Leonard S. Vincent2, Amelia A. Itnyre2, Daniel E. Clarke3, Kathryn I. Reinker2, Douglas W. R.
Danielsen2, Lindsay J. Robinson1, John N. Kabashima4, and Michael K. Rust1:

… Lenny Vincent, 21 October, 2016 - 2:45pm

Thanks, I just downloaded it.

Years ago I sent Hank Guarisco an email asking if he had any interest in the Pseudogaurax anchora find because his article only mentioned Phalacrotophora epeirae but I never heard back.
http://www.americanarachnology.org/JoA_free/JoA_v29_n2/arac_29_02_0267.pdf

… John R. Maxwell, 21 October, 2016 - 4:08pm

Good question

I don't know the answer.

… Lynette Elliott, 24 June, 2016 - 10:25am