I barely played V1, got it on discount when V2 was released, and rushed through it on Normal difficulty before hopping straight onto V2 where I got my ass torn open when I unlocked Legend/Cataclysm.
A year or so later I felt like playing Vermintide again and start from the beginning to roleplay U5’s story. I played till I finished all levels in Nightmare (except Summoner’s Peak and River Reik) and upon returning to V2 became WAY better at the game.
I think with V1, playing with their godawful bots you can’t trust to handle themselves, not having get-out-of-jail-free career skills, and being stuck with a far less developed melee system on Nightmare ended up teaching me all the good habits needed to survive Legend on V2.
My point is… it’s worth it returning to V1 from time to time. That game has a lot of good in it, and it beats V2 in terms of atmosphere and level to level story structure.