All those reasons are exactly why they're nerfing SS. It's ridiculously over powered compared to the other two at this point, so it needed balancing.
I get that, and the game is generally tuned to really not need super optimal/high DPS builds to play most content (hard/challenging/level 4 control points etc). The thing that's frustrating to me is that it's a nerf that hurts DPS when the newest content requires DPS, and its something that further reduces the way a specialization is differentiated rather than adding to the others.
On console, for the raid specifically, every further nerf hurts the ability to take it on reliably at this stage, specifically nerfs that hurt DPS (and this is a big one for the raid - basically what every person who has completed it says it hinges on). I was hoping that the other trees would get a perk added or re-worked, since looking at them, not only do they seem underwhelming in power level compared to Sharp Shooter, they also just seem underwhelming as things that actually change the way you (or at least I) play the game.
Survivalist gets (this is what interests me):
20% increased Protection from Elites (not insignificant, I suppose, but I find it's generally more about killing them quickly not worrying about getting killed), 15% outgoing healing, 10% skill cooldown (given how skills work, this is not hugely beneficial), and armor kits heal groupmates that are close.
Granted, it makes sense thematically that lot of it is added resistance/healing, but I wouldn't say that's particularly useful in the endgame content. Armor kits and basic heal skills are already strong enough to survive all content (as long as DPS is there for the raid), but those combined with these perks, still don't seem like enough to make playing the game with a tanky approach is viable. If these things meant it was more viable to drop healing skills for damaging skills, that would be great, but those damaging skills are fairly underwhelming still too.
Demolitionist gets (this is what interests me):
Group members gain 5% damage to targets out of cover (5% to all group members is strong and it happens enough to be noticeable), When armor is reduced to 0, refills all main weapon ammo (in a way this can help DPS, especially builds that benefit from armor being stripped).
Not sure if being able to choose 15% of your weapon types in any tree is enough to really make up for the nerf to Sharpshooter/general underwhelming nature of the other two? I went to the shooting range and tried switching to the other trees (fully unlocked) and yeah, it just feels like come next patch, no matter what, I'm going to feel weaker.
It's another case of, I get that it's all about balancing the game overall than about nerfs/buffs individually, etc., but I wouldn't say that Sharpshooter felt broken to me as is. In thise case, I just wish the other trees got a bit more of a bump instead to feel more important.