After having played the WD a little while I have settled on a build that allows me to do Empowered GR40 and maybe higher (I have not tried).
The idea is to stand away from the action, like a ranged character.
I am using 2-set Jade Harvester + Haunting Girdle as my main damage dealer. I am using Haunt + Draining Spirit to keep mana up and the cubed Aquila at all times.
Then I am using 6 piece Zunimassa's to get a lot of pets. I have the Zombie Dogs (3) as well as Fetish Army / Daggers (8) + Gargantuan + 15 Fetish Sycophants, for a total of 27 active pets on screen as well as the Enchantress, 28.
I am using Creeping Death to allow Haunt to last forever and re-ignite the 8 second cooldown of the Zunimassa, but maybe it's not needed.
On the weapon and off hand I use the Manajuma's which allows me to run really fast and avoid most obstacles or to get out of trouble.
I do not have any other gear at the moment or better weapon for other combinations. Since I can do GR40 I presume I am just half way there to GR90? Seems like a very long way to go.
So unless you have god tier gear its difficult to climb into those high level 80-90 Grifts. Even then it is common to use set pieces for their bonuses. Set pieces should be your aim due to how strong their 2,4, and 6 piece bonuses give. Zunimassas while good is arguably on the lowest rung when it comes to progressing in grifts, however when you have god tier gear you can use the Zuni set with better results. I would suggest looking at some of the more common builds so you have gear to aspire towards, and once you reach Grift solo lvl 50 you should be fine for hunting items and creating whatever set/build you want.