Well, many thanks for all replies.. Regarding provided example.. it's simplified on purpose, to make it clearer. I realise that those 3 actions are really not actions because they can easily be splitted into more basic actions... I provided that example not to discuss it (though thanks for that!) but to point that dependencies are helpful at planning a project. And yes, I won't be able to set dependencies for every project because sometimes to many things are changing during project. But sometimes, for me quite often, they may be very useful.
So if there is any other software, other way to get them implemented into my GTD system, i would appreciate posting that.