I'd recommend Delia, Arisha, or Miri for something like this.
If you're just focusing on getting through to endgame and teaching people system stuff and what's worth investing into it doesn't matter that much, but if you want to teach people how to deal with boss patterns at all, you should be playing a character that uses both an invulnerablity frame dodge and a block ability so the knowledge applies to any character on the roster that a viewer might pick up. Playing a character that iframes or avoids most things is wildly different from playing a blocking character that can ignore certain multihit patterns after one block but needs to learn how to/what needs to be perfect blocked.
Good luck if you do go through with it, I wanted to be a content creator for this game too but by the time I got the setup for it I kinda lost interest, haha.
Niflheim is a set of battles you might find worth checking out, it was released as optional challenge content when season 2 was done. The idea is that you can't use graces and you permenently die after 3 deaths. The first two battles also feature a sort of remade Succubus and Blood Lord battle.
It's been through a few revisions since release; you were originally unable to revive at all after dying on hard mode. At one point they removed the attack cap for Niflheim, but the bosses ended up dying way too fast so they readded it and buffed the boss hp by a lot. Currently it's just not suitable for level 80 players (that's when it unlocks) and the fights can really drag on if the party's additional damage is low. I'd recommend giving it a try once you get your free +10 gear at level 90.
It's still among my favourite content in the game, but sadly there's only 3 Niflheim battles. There's so many old bosses they could've worked with for it but they ended up going with Ein Lacher as the "throwback" mode but that gets pretty boring as it's a solo only deal.