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) 

<Fun is for Casuals> is a serious but casual horde guild on US-Hyjal. We are serious about raiding without the intense hours. Even when recruitment status is none, we will accept exceptional applications for all classes.
Our raid times are Tuesday and Thursday from 5:30PM to 8:30PM server (PST) with raid invitations sent out a few minutes prior to that.
We're interested in you if you fit the following criteria:
Raid attendance is essential. We don't want people sitting on the bench but we also want to make sure we're raiding 6 hours per week. We expect you to be available for at least 90% of our raids. Be on time and prepared for raids. This includes flasks and other consumables. Discord is mandatory and a working mic is desired. You're appropriately geared for our current content. Effort and thought have been put into your gear/gem/enchant choices. You wouldn't show up for a job interview looking like a *filtered*, why would you apply to a guild with improper gems or some insane spec? You're up to date with your class. We expect our raiders to perform to the best of their abilities. You have a computer that's not run with hamster power or requires a hand crank. Some encounters are taxing on a computer's resources so if your toon can't even handle Orgrimmar it's not likely to do well with 20+ whelps that need AOE'ing. You may be interested in us because:
 <Fun is for Casuals> uses the personal loot system. There is no loot council, or DKP. We won't eat your babies the first time you stand in something you have no business being in. Repeatedly do it and we'll break out the bibs and BBQ sauce. We provide a limited amount of consumables and flasks on hard mode raid nights.  Discord isn't a circus during raids. We're focused on the job at hand and you should be too. We don't want someone to miss a an interrupt because they were distracted by fart jokes. We are not interested in you if you fit the following criteria:
You roll on BoE items then sell them. Unwilling/unable to spend an entire evening on one boss during progression. While this is rare, it can happen. Drama queens. If you have a problem bring it up to E. This is his job. Don't announce it in guild chat or during a raid. Your issue will have nothing to do with 99% of the guild. You are 17 or younger. We try to keep guild and discord chat PG-13 but occasionally a few four letter words appear out of nowhere. Additionally, we don't want someone's mom interrupting their raiding to get homework or the dishes done. Follow the instructions at https://gow.gg/fun-is-for-casuals under the Recruitment tab if you would like to apply.

Welcome Adventurers! The time has come upon us, FINALLY! The moment in Classic WoW history us diehard, loyal WoW nerds have all been waiting for. WRATH CLASSIC! Arthas Did Nothing Wrong (ADNW) has just begun recruiting (For WotLK Classic) hard-core, casual, rp, pvp, pve, raiders, anything you can think of, you are welcomed here. Although our main focus in ADNW will be progressive raiding, 10 and 25 man and pvp content, we look to have someone for just about anything. Currently we are recruiting for our CORE 10M team composed entirely of irl / internet homies. We are in need of just 1 HEALER (Highly prefer a disc priest with a shadow off spec) and another DPS. Preferably lock or Shadow priest. We are looking to fill our B 10m team entirely, so we can pool together for 25 man’s when it comes time to crush 25m. This guild was founded by a group of tight nit friends recently, who have been around since TBC. WOTLK was our turning point in WoW, and we CANNOT wait to get another crack at this and MAKE IT RIGHT. Come join the adventure of a chill environment full of helpful hands and knowledge. Feel free to reach out to me Via Discord: Daevilmonkiexp#9239 OR Bnet: Daevilmonkie#1280 just let me know you are interested in the guild and we can have a convo! ARTHAS DID NOTHING WRONG!

About us: We were founded back in Mists of Pandaria with a primary goal to Raid and have fun within a pleasant atmosphere.
Currently we are rebuilding the guild, due to the big step back of the current state of the game. Our progress at the moment is 3/10 HC and want to go all the way to Sylvanas.
Raid days: Tuesday & Sunday, 20:00-23:00 ST
People that we need:
·         Easy-going people whose main goal is to achieve AOTC in upcoming raids while having fun without much pressure.
·         Regular and systematic players, we do not require attendancy, but we aim to create solid and regular raid team that will improve together over time.
·         People who want to improve, learn and get better at the game in friendly and stable environment.
Roles that we need:
·         DPS
·         Tank
Future plans:
We are aiming to fully clear Heroic.
Do the Raid achievements.
Create Social groups for M+ , achievement runs and help alts or mains
Re-clear the Raid with our alt as well.
Contact: Discord: TotalTunt#3017, Terravibe#2242
Website: https://guildsofwow.com/burningembers

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?