Good questions. For ease of play, and to free up points, I'm trying to survive with just one batallion (and SCD, and patrol). I've also noted that in tournament settings, my opponents have often maxed out on secondary points because it is quite easy to get rid of your troop choices when you try to keep them affordable and plentiful. So consider this an experiment. If I can get by with fewer cp, then I could possibly give up less secondary points and have more room for larger units and fun choices like my leviathan. Fingers crossed.
I'm not a big fan of ITC scenarios but I do play it for some tournaments and leading up to those events. And yes I can say from my last ITC GT with my Black Legion that anything above.... 2-3 units of Cultists just bleeds kill/kill more.
But even CA19 Maelstrom gives up 'kill anything' pretty darn easily.
I would like to hear how you do with that little CP in effect.
For Rubricae, my gut for a while had been that this was somehow workable, regardless of everything else:
1*20 Rubric (Dark Matter, Webway, deploy right in their face)
With the intent that 4*5 of them would "team up" to really be 2*10, so tackling two "things". Maybe even in Rhinos. Or a Land Raider, heh.
That final 5 could be Tzaangors or Cultists too. A sort of cavity filler foam.
But the main thrust is the big 20 for oomf, the 4*5 twenty for going after two "things" (objectives, filling two small holes, psycho/i threat), and the remainder really just being a filler for the +3 or +4 on what you'd do alternatively.
5 Tzaangors... I think you need 10. Which goes back to asking... is it even worth taking 10? You're at the cost of 2/3 of the Cultsts you'd need for your Batallion
Maybe at the end of the day only 1 or 2 Cults gets a lot of competitive play. I don't know, but it makes sense for some of them to be smaller Detachments... IE: Magic.
At least with Magic we could do a SMD with Magnus (which was what I was thinking of moving into to keep Magnus rolling.)
Something like Duplicity just screams for a bigger multi squad Battalion though.
I just hate the idea of a 'feed' Battalion as I call them of Cultists. I just really have become sick of Tzaangors and am finding you need too many of them to make them valid.
At this point in 8th edition, the only valid configuration of Cultists I found was about 30 with Abaddon. (Fearless) With recycling (sometimes). But with our new Strats, the almost constant pre game use of extra Warlord trait and Relic, it's getting tight. Especially considering our new Stratagems.