many trick can do in card games, how if you've deal with a person have a skill cheat on card games. i guess for both trick in online or offline is same and the only one can beat that's trick is luck.
You seem to forget that in online gambling there is provably fair method so basically cheating by the site operator that use a provably fair method is harder than those that dont provide it. As long as the site is provably fair and you are verifying your rolls then you will know if the site operator is trying funny things