Seismic Slam was always one of the skills that I was the most interested in and so I was fairly disappointed when a build that spams SS was basically not competitive/endgame viable.
I think your Fjord Cutter idea is good, but it sadly is restricted to one rune (and on a personal note, for me it is aesthetically not the most pleasing one).
I came up with the concept for a MotE set rework a while ago that changes the set to focus more spamming SS instead of having its focus on Leapquake (but that still is true to the fantasy of a Barbarian that is utilizing the power of the earth) and I think this might be a good place to share it.
Of course I am not expecting you to like it or to agree with it or whatever, but maybe you guys can take some inspiration out of it if you want…
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Might of the Earth set
2 set bonus
Everytime you use Seismic Slam, the cooldown of Leap, Ground Stomp, Avalanche and Earthquake gets reduced by x seconds.
4 set bonus
Every use of Seismic Slam, Leap, Ground Stomp, Ancient Spear, Avalanche or Earthquake reduces your damage taken by x% for 15 seconds, stacking up to x times.
6 set bonus
Every use of Seismic Slam increases the damage of Seismic Slam, Leap, Ground Stomp, Ancient Spear, Avalanche and Earthquake by x.000% for 15 seconds, stacking up to x times
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Support Legendaries
Lut Socks
Leap causes an Earthquake when you land and Ground Stomp causes an Avalanche
Legendary Weapon
Reduces the Fury cost of Seismic Slam by 50% and increases the damage of Seismic Slam, Avalanche and Earthquake by xxx%. Seismic Slam has a xx% chance to either cause an Earthquake or an Avalanche when it hits an enemy
^^that weapon is intended to be either a rework (or even a replacement) of Fury of the Vanquished Peak or Blade of the Tribes, or to be a completely new item.
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That would focus the gameplay of the MotE set a lot more around Seismic Slam - since you would get the coodlown reduction from each use of Seismic Slam rather than per Fury spend (and also a damage and defensive bonus from using SS) - and with the legendary weapon, you would cause a lot of havoc by procing Earthquakes and Avalanches when using Seismic Slam (rather than with Leap).
You would be encouraged touse Avalanche on your build as well, which currently is not a thing in MotE builds afaik, since you kinda have to choose between Avalanche and EQ - and since EQ deals more damage due to better support items (that also compete for the same slots iirc), most people only use EQ.
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I am not sure if you like it, but tell me what you think.