well I don't know shit about any herbs doing much for liver enzymes or any studies using herbs.
as for NAC . thats not an herb
"Cysteine is a semiessential proteinogenic amino acid with the formula HO₂CCHCH₂SH. The thiol side chain in cysteine often participates in enzymatic reactions, as a nucleophile. The thiol is susceptible to oxidation to give the disulfide derivative cystine, which serves an important structural role in many proteins.""
this amino acid promotes the creation of Glutathione in the body ..
Glutathione is capable of preventing damage to important cellular components caused by reactive oxygen species such as free radicals, peroxides, lipid peroxides, and heavy metals.
so again , No Herbs here
and yes plenty of studies have been done showing liver support and reduction of enzymes and also why these things are used in medicine , and not just bodybuilding circles .
as for your situation . of course your liver enzymes were high. you were taking Dbol. your liver enzymes elevate as a response to metabolizing the Dbol (doesn't matter what supplement you were taking or not). thats just the liver doing its job. NAC isn't going to prevent the liver from doing its job.
IF you really wanted to know if NAC helps lower liver enzymes you would need to take your Dbol .. then stop taking it. then wait 3 weeks, then get liver values checked, then take NAC for 5 weeks, then take liver values again and see if they came down substantially or not .
again, no supplement is going to stop liver enzymes from going up in the first place during the metabolizing of oral AAS . thats not how liver support works. they may help the oxidize stress during the metabolic process, but they don't stop the process itself (and the process itself includes elevation of enzymes).