The HD is dosed at 25mg because the Phreak pills combines two hepatotoxic substances. SD is literally the worst "designer steroid," with regards to liver health, combine this with another hepatotoxic substance and you are playing with fire to begin with; combining more HD into the mix is insane. In other-words the HD in Phreak is not under-dosed, when its combined with 30mg of SD.
Have you ever done a cycle before? Whats your cycle history? There is no normative dose for HD, its dependent upon body weight, etc. For instance say you weighed 180 lbs, 100mg of HD is way to high, unless you are an experienced veteran with a huge list of cycles under your belt who pop's prohormones like cracker-jack. Most people recommend running HD @ 50/50/50/75/75/75, especially if your new to cycling. It's always a good idea, regardless of substance to assess your own individual tolerance. Inversely a lot of people don't run HD beyond 75mg because there is a huge increase in side effects, and lack of gains; of course this is predicated upon weight, experience and subjective reaction to the exogenous hormone being ingested. In essence some people experience negative side effects over 75mg, some do not. All I am saying is assess your tolerance, to gauge how your body reacts and plan your cycle from there.
"Preloading" with Liv52 and Milk Thistle, is like dropping a splash of tap water into the ocean, it ain't going to do much, but I would do it anyway, its always better to be safe than sorry. What are you planning on running for your BP, because its definitely going to be elevated especially with the doses you are proposing, what about LDL cholesterol level, prostate enlargement, etc.? If your going to take a preventive supplement why not take a combo product that provides a broad spectrum of overall health benefits, why confine yourself to exclusively worrying about liver health.
You are free to do what you want, figured I'd just throw my 2 cents out there. Good luck and get blood work done.