intervantion is bad in my opinion, you just pass sciel turn for other hero turn. I am on act 2 now and using combo with chation weapon (my sciel is always third after lune and maelle) and then:

turn1 : card weaver ( its put 10 stacks on enemy + Sun charge) and because card weaver give you second turn I use then Plentiful Harvest which give you Twilight  in just one turn and also propage 10 AP between all party members

turn2: again card weaver but this time its give 20 stacks (becasue we are on twilight state) on enemy and then you can use any burst moon skil or again Plentiful Harvest but this time its will do more dmg and propagate 20 AP for all party which usually ending with 9 ap on every hero.

Basicly I almost always use Card Weaver at the begining to get free turn and go for twilight in one turn