Spoiler:
Saying Kaboom is a better knockback than SM and BO knockback is a little misleading, yes it has further range and is easier to time but those knockbacks don't lock you out of half your abilities + 360 points of stats for 10 seconds or root you in place during the explosion/flying gobbo animation.
Pierce defenses is great for sure. Order has easier access to it so doesn't seem unbalanced to me, and it's a tactic slot. These jack of all trades SH builds seem to use a lot of those.
Melee interrupt doesn't work in Squig Armor while WL interrupt is AoE, pretty important differences. On demand move speed (assuming you mean Run Away!) does not work in Squig Armor. You leave out pretty important details in your comparisons, like WL armor debuff is undefendable so if you are getting focused by a WL you will almost always have it on you, wheras SH ini debuff isn't useable in SA which makes it SIGNIFICANTLY less likely to get used on you by a stabbity SH, pretty big difference in usefulness.
It seems like you wrote down a list of every ability SH has access to with no real regard for how to fit them into a spec or how ineffective it is to actually try to mix some of those into any type or rotation when half of them lock you out from the other half and a bunch of your stats. That build you linked seems borderline useless to me personally. In what situation is sacrificing all that stabbity stuff for the healdebuff a good call? If you are solo you won't use it because you won't be able to do good dps during the duration of the healdebuff due to being locked out of SA (yes, theoretically you could use it at the end of the 10 second CD, but that means you just spent 10 seconds without access to all of your burst so the enemy most likely isn't going to be low enough on HP for your healdebuff to matter before the duration ends), and if you are in a group almost any other healdebuff in the game will be easier to use and won't have so many negative side effects on your group's build and combat effectiveness. If you want to spam healdebuffs so bad you are willing to constantly leave SA and give up those mastery points I think a ranged spec is probably a better fit.
Honestly, how many of you guys are seeing SHs drop SA mid-combat to use all these ranged abilites? I drop it for kaboom because I am forced to and ranged snare/Run Away! if I'm chasing someone and pounce isn't working, that's it. If I'm already locked out of SA from a kaboom then sure I shoot stuff but that's just what I'm forced to do while I wait for SA to come off CD, not my ideal strategy. I see you play SW so I assume you are thinking of how those stance mechanics function when considering how stabbity plays. 10 seconds of losing SA is a lot longer than 5 seconds of losing stance switching for SW (if I tried drop SA to use an armor debuff and ini debuff against a geared guardian WL I would not make it the 10 seconds to get back into my SA), and you don't get locked out of as many abilities when changing stances either, many SW abilities can be used in 2 stances, it makes a difference. Also don't forget all the stats you lose, the 120 wounds basically gives all your ranged attacks the fine print of "If at full HP in Squig Armor, also deal 1200 morale damage to yourself" and guarantees that damage if you choose to start fights in gobbo mode instead of SA so you can open with all those ranged debuffs. Another big difference between the 2 mechanics is SW stance dancing doesn't use a GCD while entering SA does. So in this hypothetical world where stabbity SHs are constantly stance dancing to utilize all their ranged core abilities regardless of how poorly that performs in reality or how long it locks them out of all the stuff they actually spec'd for, they are also constantly using GCD's to do 0 damage, 0 healing, and 0 utility, doesn't seem like an ideal strategy to me.
I do agree that a stabbity SH has a large variety of tactics they can switch out for different roles which make them very versatile without needing to respec, but that doesn't affect how strong any SH can be in 1 spec at any time so doesn't really seem like something to balance around IMO. Their versatility without needing to respec is really a side effect of the way their mastery trees are setup IMO, there is only 1 melee tree for SH so when you max it you pretty much have access to everything a melee SH will need, it's not like WL where you can throw pounce into a different tree than guardian to make them spend more points for it, although maybe there is some creative way to put must have stabbity abilities/tactics in other trees if that's really a goal anyone wants to pursue.