Sorry for delayed response. Looks like I missed a lot of discussion, can't address everything said but have a few comments.
First I like the idea of buffing heal companion to more like savage defiance, though since this is a low level pick it does nothing to address making SC rangers preferable, which is why I think you need a better healing buff on Bonded Fury. Like could do hardy companion => robust companion and add more healing on bonded fury, alternatively hardy companion gives heal 10+health per 3s for 15s, hardy, and bonded fury gives robust for stacking.
Have you tried changing Bonded Fury to give all tier 3 inspirations? Then playtested it a bit? I think that would be enough to make SC ranger competitive. And it sounds overpowered because "all tier 3" but it's on the pet so it really isn't. It will still be worse at combat than any properly built character including companions by a ward margin, and keeping it up requires most of your bond. I'm honestly not that familiar with most of the SC bond regeneration, though I know distraction training doesn't really work as is. And I'm pretty sure adding pet on-crit resource regen will not work in the encounters you need it to work without intuitive. So here is a proposal for bonded fury
2 bond, gives all tier 3 inspirations for 30 seconds, 50% chance return bond on pet crit
Keep it .5s cast, 0 recovery. If you add recovery you are really going in the wrong direction with SC ranger. Besides, it is a passive buff, not like an attack ability, doesn't make sense to have a recovery.
The 50% chance is just an educated guess, would have to playtest it. But the on-crit bond return is really only going to work with intuitive except in easy encounters. Intuitive + Energized will give the pet some combat utility so it can do some interrupts, swift some mobility, and robust some tankiness. It still won't do a lot of damage but it will be useful at least. Alternatively the on-hit/crit seems all right. I think making the pet better at combat is what can make SC ranger something you'd actually want to pick, as the pet is really the identifying hallmark for the ranger.
Or if you don't like robust since it isn't stackable, 2 bond, gives intuitive, energized, swift, brilliant, courageous, hardy, +10 (or more) health per 3s for 30s, 50% chance return bond on pet crit
I don't think having Bonded Fury pseudo-mandatory is that big a deal. You basically get four L8 picks (2 at 16, 1 at 17, 1 at 18) and there are five L8 choices. And I'd think most builds probably wouldn't pick both twinned shots and whirling strikes. Or if they wanted to, less pet-focused builds could skip Vengeful Grief (or Great Souls).
I like the Vengeful Grief 25% action speed buff, though could just make it an enhanced fury on pet death which is similar effect and matches the description of the ability better (fury with tenacious / nimble or whatever)
Having some kind of healing available to the ranger himself would also be cool, not strictly necessary but could make melee rangers better. Like add to bonded fury a "ranger receives 15% of pet damage dealt as healing".
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I know you think I'm basing all these suggestions on solo play but I'm not. Solo is what initially made me notice how bad SC ranger is compared to MC, but the same holds in parties, and I've played with parties quite a lot, though recently more focused on solo. The SC shortcomings just aren't as noticeable in parties because you have other characters to pick up the slack. But the fact a build can do okay in parties doesn't mean anything by itself. I could make the worst build possible and it would still do okay in well-built parties because if this is a game where some classes can solo (and it is), then you really only need one truly well-built party member and the rest can just stand there getting murdered. I know that's an extreme comparison but you probably get my point.
For role comparison,
I did mention a ranged crit build centered on stunning shots for CC is the only real reason to consider a SC ranger.
Though even a ranged CC build has good (better imo) alternatives like ranger / monk (instruments of pain, stunning surge) or ranger / chanter, ranger / cipher, both of which don't have this specific method of single target CC but have arguably better ones available like mental binding, thunder rolled like waves on black seas etc., in addition to other resources like better healing, summons, etc.
For ranged DPS, ranger/cipher is better, ranger/chanter (sure-handed ila + energized + summons), probably also ranger / rogue and ranger / fighter
For melee striker, ranger/cipher is better, ranger/barbarian is better, ranger/fighter, ranger/wizard, ranger/monk, probably ranger/priest and ranger/rogue (haven't played rogues that much outside of parties)
For offtank, ranger/cipher, ranger/fighter, ranger/barbarian, ranger/paladin, ranger/monk, ranger/wizard, ranger/priest all better
For tank, no combinations are ideal but same listed above are better
Parties or solo, there is presently very little reason to pick a SC ranger over something else. And I didn't even mention the combinations without ranger, like SC monk, monk/fighter, monk/barbarian which are way better at striker, offtank, and tank roles, or devoted/troubadour which is better at ranged dps. (And I may be arguably off on some specific comparison because I haven't played every single one of these, not the point, the point being there is virtually always a better choice)
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And I know you like Heart Seeker, and *maybe* in a party that is a good enough reason to have a SC ranger, at least in encounters where enemies heal a lot, but generally I think you are better suited by something else.
My perspective is this: anything that requires 4 bond is just going to be really expensive in the hard encounters (megabosses, DLC bosses) where you will run out of resources very quickly if you use the active abilities, hence active abilities becomes less important than things like stacking accuracy to hit with normal attacks or stacking deflection and healing to tank or CCing the enemy. Potions of enlightenment address resource loss somewhat, so that you can still use *some* abilities that require limited resources, but I've found you can sustain at most one 12s/bond duration ability (with max INT and INT inspiration). You can sustain multiple abilites in some cases if the durations are longer and/or there is resource return or ability to extend the ability (like blood storm on crit). Generally it is much better to use your resources on long duration passive abilities you can sustain (like hardy companion / bonded fury / shadowed hunters, or swift flurry with monk, or blood storm + stalwart defiance for barb) than using on twinned arrows or whirling strikers or whatever.
This probably isn't true in easy encounters, but it is the hardest encounters that function as gates for builds and therefore it is important to make sure a build has a chance of surviving the toughest encounters, moreso than how it performs fighting mooks.