I apologize for saying this but Sinister Labs is very dependent on your roster, especially Epic level. RNG also plays a critical role who you’re up against. Yesterday was a breeze with an R4 5* ArchAngel.
I’ve done all Epic and Master Sinister Labs to date with no items used. Wasn’t the same with MODOK’s labs when I was much weaker. Sure, I’ve exited several times if the RNG gives difficult match ups but having a strong roster helps big time. Used boosts a few times. Just really time consuming but doable when you’re roster can tank the nodes.