I don't think wyches have actually suffered "to much" (still a bit but they are still great! I run a largly wych cult army supported by the same Archon as you have up there with 3 venoms with 4 blasterborns. Each wych squad gets a Haemocules and more often then not I can get into assault and they will do well. You just have to maximise cover and I like to play wyches (same as I did in 5th) not as a tarpit, they won't last as long now, but as a squad to wipe out another squad, use 2 squads of 10 against a 10 man marine squad and cut them down when you win combat! This even worked against a blood angels list recently! So don't lose faith.
Blasterborn have suffered BUT are still the most legit anti tank I think, Ravagers have got better and are still very good but 1 shot and they go down, venom goes down you might have a full squad left to shoot after!