I got to the second level of a rotten lower ailing loran root chalice and it's full of super strong NPCs. It's rough.
You may already be aware of this, but high depth (difficulty) Chalice dungeons are better taken as separate to the main game. The higher difficulties of dungeons are meant for characters that should be in NG+. You'll have a rough time if you're playing a character that just recently finished NG.
So I'm thinking of doing a dual blood tinge and arcane build. Is relying on a fire arm as a good source of damage reliable?
I don't have any experience with Arcane yet, but as for relying on a firearm for your damage, I don't quite think it would work. The highest Bloodtinge scaling firearm was only doing roughly 150-200 damage with regular shots with 50 Bloodtinge. ~700-800 with buffed shots to weak-points.
Someone can correct me if I'm wrong, but i don't think it would work with relying on a firearm.