Totems are just buffs with a physical manifestation in the game world. Healing Tide Totem and Tranquility are nearly the same skill. Renewing Mist and Healing Stream Totem are nearly the same skill. Yes, there are definitely differences that impact how they play out, but it’s a bit silly to say "Shaman’s identity is that when they press their version of tranquility or renewing mist, their tranquility and renewing mist works a little differently, but they also get a little 3D object in the world "
Is there any reason healing rain or a druid’s efflorescence couldn’t include a little 3D totem in the game world? The concept of something being a “totem” is arbitrary and basically ONLY a skill-type designation to determine what relatively-boring talents get to affect what skills. I mean, I guess I would call it distinct and unique, but that the implications of it are just not that significant. They could easily remake every totem to just be a skill/buff/cooldown you cast that emanates out of your character (or target the ground like healing rain/spirit link), and the class would play basically the exact same with negligible differences.
I made sure to start my post by stating I was describing the theme of the class specifically and made no comments on gameplay mechanics whatsoever.
Based on most people saying that the “stormbringer” hero talent tree should go to elemental and enhancement, I don’t think most folks have gotten it through their head what resto’s theme really is. Would YOU agree that if the spec’s theme is water/flood/tides/waves/rain/clouds, then between enhance and resto, resto is the clear choice for getting the Stormbreaker hero talent tree? Sure, all three specs have a claim, but stormbreaker is the only one of the three that relates to how every single restoration shaman is healing (thematically).
To answer your question on what their niche is, I would argue that rshaman’s niche in the game is that it is the easiest and most forgiving healer to play and is a fantastic entry point for people looking into getting into healing while playing optimally. You can think of it as the beastmastery spec of the healers.
Compared to resto druids, it is a lot easier to deal optimal damage (avoids shapeshifting, melee range), it is way more forgiving if you forget to get riptides out compared to lifebloom, it is far more reactive and has a mastery that allows you to catch up easier than the proactive-nature of druids.
Compared to mistweavers, it is far easier to understand the relationships between your spells and passives, which can be extremely complex to optimize. It is far easier to do damage, as you do not have worry about your positioning as much and are ranged.
Honestly this post will get long if I go through everyone, but compared to preservation, you do not have to worry about using combos effectively, or having your potent heals be on moderate sized cooldowns. Disc you don’t HAVE to do damage if you do not want to, holy paladin no melee, less impactful and intricate cooldowns. Etc. Instead of something like pain suppression or ironbark, rshamans have 6% damage reduction on perma-uptime earthshield. They sacrifice burst on-demand damage reduction, for consistent perma-DR. Their mastery helps with catching up when behind.
All that is to say: for me what makes rsham unique is its simplicity and forgiveness. Beast mastery, affliction, and balance all do damage over time, but it’s clear that beast mastery’s niche is it’s forgiveness and ease of use, not how intricate it’s damage over time is compared to those more-intricate specs. I don’t have to tab-target-reapply the correct dot in the right timing, to do effective AOE damage, I just push multishot. And if I stop pushing buttons for a little, my pets are still doing damage.
I am certain it is intentional that Rsham doesn’t have their version of atonement, or echo, or ancient teachings. There’s still some room for skill ceiling, like cloudburst, but the simplicity and forgiving nature of its toolkit IS its niche, in my opinion, if we’re talking game play.