Do you give them different Domains depending on which sorcerer king they work for?
And just a quick Addition on thegreat sword Topic: since there is no reasonablenon Magic material other than steel to make a great sword of, you could just leave it at 2w6 and still be fine

but thats just me, being a bit pendantic.
Obsidian Greatsword.
In 2E all the Templar's had the same features and they were more martial than the existing Clerics (better weapons and armor). That is kind of reflected in the war domain. Each Sorcerer King could grant an additional domain I suppose but they were not really strongly tied to a philosophy so its hard to assign them due to a lack of 5E domains (it was easier in 3.5). I'm using some of the 5E domains as placeholders as the elemental domains have not been done yet.
Using 3.5 terms some SK's do stand out a bit.
Elemental clerics get the elemental domains.
Hamanu War, Strength
Nibenay Knowledge, Darkness (Shadow King)
Lalal-Li Puy Plant, Animal
Abalech-Re Chaos, Trickery
Kalak Tyranny, Evil
Gets a bit harder for the SK's of Raam and Balic (Raam War+ something else, Balic no idea). Those domains do not exist in 5E yet (3pp some of them do). so I made do with the 5E PHB.
If dedicated elemental domains are made I suppose you could give the SK's different domains (Hammanu War, Nibenay Knowledge, Abalach Re trickery, Lalali-Puy Nature etc).
The rules can evolve as new things are added a'la SCAG vs PHB, new things should be organic or make sense though and not contradict stuff (artificers making decanters of endless water, artificers in general though).