personally swirling axe for the berserker is better than the swords from Freya - also if you check the screen at the end it tells you what the highest DPS skills are, from memory on the berserker it will be sentinel from Thor, Golden disks and Swirling axe
Keep in mind the game is not finished or at a full release version. We only have access to a demo that only has some features available while most likely has bugs/errors and isn't optimized yet. Hopefully the game's official release version will be changed to run on the steam deck for you by then (as long as the steam deck meets minimum system requirements of course).
If I am not wrong that class can kind of create a feedback loop, multicasting, with cast a skill when becoming enraged, and become enraged on casting a skill, then add the on crit cast, it can become crazy.
me personaly think the 2nd difficulty is by far not worth when you want to farm gold for your passives, the 2 runes kombined are so much easier than that,´and gives 10 oder 15% more currency. -- i tried the 2nd difficulty a few times now but never got even close to the final boss, mostly the "muting" objectives destroys me or a few minutes after i got them down. but then i got overwhelmed. i think i should try your strat with freya normaly i did it with thor and crit.