You shouldn’t need to do bounties (unless you really want to). The Barrowholm level 65 items only require Friendly, so you already have that. You can start on Elite and go back to Normal/Veteran at 65 just to pick up the interim gear from Barrowholm before getting the rest at 90.
The only faction I did bounties for was Rovers (so I could unlock the Mogdrogen shrine on normal). I may have done a couple for Barrowholm on Ultimate to finish off to Revered, but if so, it didn’t require much. Simply playing (and in my case, fully exploring maps/all areas) and doing quests got me all the rep I needed.
I wouldn’t worry too much about resistances in Elite (especially if they’re close to maxed) unless you feel noticeably squishy. If so, just add a few components to round things out.
Thanks for the vote of confidence in my guide. I may or may not make more guides at some point (been playing a lot of Subnautica recently). In the meantime, if you’re looking for melee, I’d recommend checking out Stupid Dragon’s 2H Lightning Elementalist build.