Who said anything about guessing? Im sure there will be some kind of UI or something to tell you EXACTLY how much damage you will be doing.
It is a completely different system, and anyone who passes judgement on one tidbit of information without even hearing the complete context it is in isnt giving the game its justice due. You may be right, the system may be bad, but you also may be wrong and the system will work far better than spell making ever did. Considering the apparent direction and the people making the game, ill put my money on the later not the former.