As far as damage goes, Cycle multiplies your damage by 4x while Shadowhook multiplies it by 2.5x outside Simulacrum, and 5x inside of simulacrum. So Cycle is always going to result in higher overall damage, but not by a *huge* amount on average if you take Simulacrum. For 12.5% Sim uptime it's around 42% more damage to take Cycle.
The damage from Cycle is more reliable, though, and is never "wasted". Also, for many Rathma builds that skip Simulacrum for e.g. Devour or Bone Armor, Cycle is a ~60% damage increase.
Personally, I have found it to be very viable to run Cycle instead of Shadowhook, and use Siphon Bood/Blood Sucker in conjunction with Reaper's Wraps to solve the essence issue. Compared to Bone Spike + Shadowhook, the essence gain from using Blood Sucker is much better as long as you have reasonable density, and you do more damage as well. Under typical GRift density, you can instantly fill your essence bar just by tapping Blood Sucker and just crap out maxed out Singularity mages constantly. The only downsides to this approach are on longer rift guardian fights at high GRift level, and higher ramp up time when you are stuck with poor density. But for just clearing to the guardian I like it a lot better; it's significantly more damage, has better essence regen, and it lets me take Devour and Bone Armor for better healing/toughness without worrying about needing Simulacrum.
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It is because of essence generation, period.
As far as damage goes, Cycle multiplies your damage by 4x while Shadowhook multiplies it by 2.5x outside Simulacrum, and 5x inside of simulacrum. So Cycle is always going to result in higher overall damage, but not by a *huge* amount on average if you take Simulacrum. For 12.5% Sim uptime it's around 42% more damage to take Cycle.
The damage from Cycle is more reliable, though, and is never "wasted". Also, for many Rathma builds that skip Simulacrum for e.g. Devour or Bone Armor, Cycle is a ~60% damage increase.
Personally, I have found it to be very viable to run Cycle instead of Shadowhook, and use Siphon Bood/Blood Sucker in conjunction with Reaper's Wraps to solve the essence issue. Compared to Bone Spike + Shadowhook, the essence gain from using Blood Sucker is much better as long as you have reasonable density, and you do more damage as well. Under typical GRift density, you can instantly fill your essence bar just by tapping Blood Sucker and just crap out maxed out Singularity mages constantly. The only downsides to this approach are on longer rift guardian fights at high GRift level, and higher ramp up time when you are stuck with poor density. But for just clearing to the guardian I like it a lot better; it's significantly more damage, has better essence regen, and it lets me take Devour and Bone Armor for better healing/toughness without worrying about needing Simulacrum.