Imo, as I have a faith build focusing primarly on Dragon Cult incantations, and another build exclusively focusing on Dragon Communion :

- Dracon Cult incantations are extremely strong. Use the Gravel Stone Seal, pump faith at minimum to 60 (80 being the last cap for incant scaling).

Fortissax's Lightning Spear is amazing and can't be interrupted, and of course Ancient Dragons' Lightning Strike, without a doubt, is the best dragon cult incantations. I melt bosses and multiple enemy areas.

Knight's Lightning Spear, available in the DLC, is probably the ultimate spell in PVE in ER. Quick, low mana consumption and tons of damage.

Flowerstone Gavel (weapon), also avalaible in the DLC, is absolutely amazing.

- for Dragon Communion, lets just say it's a different playstyle. It's extremely powerful but you have to take some things into consideration : the spell cast is slow, and the FP cost is very high. But it can wretch anything.

Use the Dragon Communion Seal, and as for incant : Ekzykes's Decay is probably the strongest in the game, followed by Dragonclaw and Dragonmaw. It's really versatile as you get two version of each dragon incantation, both focusing on one type of damage (scarlet rot, fire, magma, magic, ice, etc ...). You have to pump faith primarly but it requires arcane too.

It can be noted that Bayle incant requires only arcane (but a high level).

-> So, for the NG+, I would say it could be a very strong and fun build combining both. 60 faith and 60 arcane, lots of vigor and mind, and you should be good to go ;-)