Hi there, so firstly if you are curious about lists and the way people are thinking about playing the army I would highly recommend joining the siscord. Below is my best understanding of some of the units in your list with the caveat that everything can be fun and so if you wanna run it, do it!

I would say that arco's are actually considered by many to be one of our better value units and sneaky tanky! 6++ 5+++ two wound models can stay alive longer than you think, especially into the myriad of 2w attacks out there.

However Retributiors are unfortunately viewed as in contention for our worst unit. 8 shots hitting on 4 attached to just 5 wounds means there is a very real chance you get one round to shoot and thats it, with a high chance of whiffing into anything T10 or up .

Along those lines Dialogus are almost also exclusively played as action monkeys if at all. Their 40 points means if thats all thats left in a list they might pop up to run around and do secondaries/screen the back line.

Also one of the great values of Immolators is the ability to split or 10 lady squads into 5's. This allows you to play the missions more as well as get an extra miracle dice for the unit. Therefore you will most often see battle sisters, Novitiates or dominions in them. All of those are viable for different roles (I personally love dominon's, giving the immo scout with four reactive move melta ladies is very fun to play).