Honestly it shouldn’t be that bad. You’ll just have to scale up your Shadow Rend casts with how much gear you have. There’s -4 cost in the tree with no hoops and you get 20 mana regen a second from just 3 T5 regen affixes. If you use the smoke bomb node that’s another -10 cost.
While leveling I image the ability cadence will be Shadow Rend > Chakram > Chakram. Then once you are fully geared you shift into Shadow Rend > Shadow Rend > Shadow Rend >Shadow Rend > Chakram. It should be a natural progression slowly adding more shadow rends as your gear gets better .
For a 16 cost shadow rend at 2 cast per second over 4 total casts that’s:
(40 mana regened + 8 mana from shurikens) - 64 mana spent = 16 mana lost
16 mana bleed isn’t particularly bad in a high regen build but adding in smoke bomb makes mana maintenance even easier.
With smokebomb’s -10 and that’s:
(40 mana regened + 8 from shurikens) - 24 mana spent = 24 mana gained
The smokebomb node is actually so strong you can itemize out of mana regen entirely and just use the native 8 flat regen everyone gets to 0 out mana cost.