Sorry I missed the Assassin thing. I read it, and then forgot it.
In my experience, Assassinate has not been nearly as helpful as I imagined when I read it. To get surprise, you generally have to put some distance between yourself and the party, and a bunch of things have to go right (5e is not generous with surprise), and getting advantage in the first round is normally pretty easy for a rogue with decent Stealth. Assassin is great flavour for a certain kind of character you want to play, but that doesn't seem to fit your character terribly well as it's more a social finesse type. Your guy sounds more like a Swashbuckler (foolhardy and dangerous on their own)/Scout (natural loaner) or maybe even Thief type. I'm partial to Scouts because they make you such a skill monkey, even more so than multiclass skill monkey types like Bard/Rogue or Knowledge Cleric/Bard.
Since you are dropping Goliath, I'll drop further rants on Tavern Brawler but I'd still consider going full on Orc if you want to go heavy on the grappling stuff, maybe still consider Orc as Powerful Build is helpful for dragging big heavy beasts you've grappled. Sure you don't get Savage Attacks & Relentless endurance, but you get all the other thematic elements, and maybe your DM will still let you take Orcish Fury (seems like an oversight it wasn't made available to Orcs as well).
I also get the Tough habit is a tough one to break (you see what I did there? ;-). I'd not underestimate the benefit of Durability (which still gives you a +1 to Con) over Tough when you have crazy high constitution (which you should totally go for).
I didn't mention the popular Barbarian feats as I figured you'd considered and rejected them, though somehow I did totally forget about Great Weapon Master, which is an such an obvious thematic fit and classic Barbarian choice I feel silly about it. The other two that are less of a thematic fit though mechanically fit well with the theme are the Barbarian classics: Polearm and Shield Master. Both also give you something to do with your bonus action on top of other useful features (AoO all the time for former and the grappler's favourite: shove as a bonus action). One feat that is a bit off the wall but would make sense with some of what you are going for here is Prodigy. It's only available if you go half-orc, but would give you even more proficiency (making Reliable Talent even more useful) and another expertise.
I do get the importance of making choices that reinforce your thematic objectives, which is why I was trying to offer options that lined up with your themes as I understand them. I think there are other boons are as good a fit as Perfect Health and honestly, the "Gruumsh won't let you die thing" lines up a LOT more with Zealot than Bear Totem, particularly with Warrior of the Gods, and if you go up to 14th where you can combine it with Rage Beyond Death makes Relentless Rage seem comparatively frivolous.
Anyway, I think no matter what this is going to be a blast for you. The jarring leap from Wizard to Barbarian/Rogue should be very refreshing.
I am presently playing a halfling rogue2/barbarian3. I utilize unarmed defense My non combat carry is a shield and javelin which are dropped/thrown at the start of combat. I also have two scimitars that are drawn once combat starts. I have him already planned out to 20 (if he lives that long) he’ll end rogue11 barbarian9. I also went totem bear and plan to go assassin once I get there. I’ll be running savage attacker, dual wielder, tough, and asi’s It’s a pretty sweet build Hope you enjoy it as much as I do
If you've got a shield, why go dual wielder? Honestly, with an 11/9 split, even with the extra ASI from Rogue, I thinks extra ability bonuses are going to be worth more than most of those feats.
The shield/javelin combo is pre rage. Dual wielder gives me that little ac bump and once I pick it up I can switch a scimitar out as I may need to. As for feat vs asi you have to build the character based on the group you’re with, type of campaign, and how your DM works.
If you're doing a multiclass into rogue, and starting at higher level, why not start rogue? you miss out on 4 hp, but gain a skill. You would also have proficiency in dex/int saves instead of str/con. Con saves are nice, but so are dex.
I'd love to necro bump this topic and get some thoughts on the recent rogue subclasses in Tasha's and multiclass options with Barbs. Soulknife in particular seems to compliment a grappler barb build with the ability to add to skill checks, the ability to summon a weapon that you can actually sneak attack with (for the unarmed barbs), and teleportation as a gap closer. Thoughts?
Sorry I missed the Assassin thing. I read it, and then forgot it.
In my experience, Assassinate has not been nearly as helpful as I imagined when I read it. To get surprise, you generally have to put some distance between yourself and the party, and a bunch of things have to go right (5e is not generous with surprise), and getting advantage in the first round is normally pretty easy for a rogue with decent Stealth. Assassin is great flavour for a certain kind of character you want to play, but that doesn't seem to fit your character terribly well as it's more a social finesse type. Your guy sounds more like a Swashbuckler (foolhardy and dangerous on their own)/Scout (natural loaner) or maybe even Thief type. I'm partial to Scouts because they make you such a skill monkey, even more so than multiclass skill monkey types like Bard/Rogue or Knowledge Cleric/Bard.
Since you are dropping Goliath, I'll drop further rants on Tavern Brawler but I'd still consider going full on Orc if you want to go heavy on the grappling stuff, maybe still consider Orc as Powerful Build is helpful for dragging big heavy beasts you've grappled. Sure you don't get Savage Attacks & Relentless endurance, but you get all the other thematic elements, and maybe your DM will still let you take Orcish Fury (seems like an oversight it wasn't made available to Orcs as well).
I also get the Tough habit is a tough one to break (you see what I did there? ;-). I'd not underestimate the benefit of Durability (which still gives you a +1 to Con) over Tough when you have crazy high constitution (which you should totally go for).
I didn't mention the popular Barbarian feats as I figured you'd considered and rejected them, though somehow I did totally forget about Great Weapon Master, which is an such an obvious thematic fit and classic Barbarian choice I feel silly about it. The other two that are less of a thematic fit though mechanically fit well with the theme are the Barbarian classics: Polearm and Shield Master. Both also give you something to do with your bonus action on top of other useful features (AoO all the time for former and the grappler's favourite: shove as a bonus action). One feat that is a bit off the wall but would make sense with some of what you are going for here is Prodigy. It's only available if you go half-orc, but would give you even more proficiency (making Reliable Talent even more useful) and another expertise.
I do get the importance of making choices that reinforce your thematic objectives, which is why I was trying to offer options that lined up with your themes as I understand them. I think there are other boons are as good a fit as Perfect Health and honestly, the "Gruumsh won't let you die thing" lines up a LOT more with Zealot than Bear Totem, particularly with Warrior of the Gods, and if you go up to 14th where you can combine it with Rage Beyond Death makes Relentless Rage seem comparatively frivolous.
Anyway, I think no matter what this is going to be a blast for you. The jarring leap from Wizard to Barbarian/Rogue should be very refreshing.
I am presently playing a halfling rogue2/barbarian3. I utilize unarmed defense My non combat carry is a shield and javelin which are dropped/thrown at the start of combat. I also have two scimitars that are drawn once combat starts. I have him already planned out to 20 (if he lives that long) he’ll end rogue11 barbarian9. I also went totem bear and plan to go assassin once I get there. I’ll be running savage attacker, dual wielder, tough, and asi’s It’s a pretty sweet build Hope you enjoy it as much as I do
If you've got a shield, why go dual wielder? Honestly, with an 11/9 split, even with the extra ASI from Rogue, I thinks extra ability bonuses are going to be worth more than most of those feats.
The shield/javelin combo is pre rage. Dual wielder gives me that little ac bump and once I pick it up I can switch a scimitar out as I may need to. As for feat vs asi you have to build the character based on the group you’re with, type of campaign, and how your DM works.
If you're doing a multiclass into rogue, and starting at higher level, why not start rogue? you miss out on 4 hp, but gain a skill. You would also have proficiency in dex/int saves instead of str/con. Con saves are nice, but so are dex.
I'd love to necro bump this topic and get some thoughts on the recent rogue subclasses in Tasha's and multiclass options with Barbs. Soulknife in particular seems to compliment a grappler barb build with the ability to add to skill checks, the ability to summon a weapon that you can actually sneak attack with (for the unarmed barbs), and teleportation as a gap closer. Thoughts?
You can use strength with finesse weapons, meaning you can use strength with a rapier and get your full sneak attack damage and rage damage.