As the title already said I'm needing help understanding how to make the build like the guide says, i somehow need to get the full set bonus of bones of Rathma but i also need the full Captain Crimson's trimmings bonus for cd reduction i can get that with ring of royale grandeur but i also need to use fate's vow helm but if i use it i cant get the full Bones of Rathma set bonus or Captain Crimson's trimmings bonus. 
If anyone know how i can get that build to work please say how, I'm open to any suggestions.
Link to the guide I'm  talking about: https://www.icy-veins.com/d3/necromancer-rathma-army-of-the-dead-build
(this is my first post on icy-veins and i don't fully understand if I'm doing this right) 

Raid/Class Spots Are Open To Any Applicant If The Player Is The Right Fit
A guild formed with an ambition for progression and a love for M+ we decided to make the move from Silvermoon Alliance and form a guild to take our focus to the next level, Cutting Edge in 10.1 being the next step.
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Hello everyone,
Last patch gave us 40% and 10% damage increase on ray of frost and glacial spike
Does anyone know of these changes make them relevant ?
Should frost mage play with these or one of these now ?

[H][Draenor][Healer problem] was founded at the end of BFA and reinforced recently with a a group of old friends experienced in mythic raiding. We are bound by ambition to build a strong core of focused players for mythic progression while valuing players over the progress itself. We offer a mature, fun and caring, yet focused environment, with respect to real life responsibilities.
At the moment we are looking for a couple friendly but committed players to complete our mythic team.
 
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I am going the corpselance support build for Necromancer and the build has me taking Corpselance with Brittle and the pestilence set on top of that, if I were to take off the ability Corpselance and change it to another ability say for example Bone Spikes with Frost spikes, would the damage decrease an amount that it would not be worth it?