Skill could get a 10% damage reduction to bring it in line
Exactly, with all spells in game and accessible to all, it is a hell of a lot easier to balance them. With a very small percentage of people having skills they cannot be balanced.
Example 1 - With books being rare:
FF finally drops, all the wizards in the guild jump for joy , it gets handed to highest roller(or most deserving blabla). The wizard then goes to try it out, find it absolutely amazing, level's nice and quick and destroys people in PvP.
People getting killed easily by this wizard then complain that it's too powerful, Sam does his magic to check if this is true, see's how it is and finally decides yes it is too powerful. The wizard then asks why it was nerfed, starts crying that its now useless(in which it isn't its just not stupidly overpowered like it was) and starts saying why did they bother to spend all the time getting the skill if it gets made useless(again it isn't useless).
Example 2 - With access to all spells:
Everyone is happily leveling, excited about being able to reach the next level and getting a new spell to use. Many others already have it, but the slower levels are that more excited that they finally get a cool spell to use.
A huge fight breaks out with everyone attacking each other with all these accessible spells, to which some are showing how overpowered the skill is and others doing less damage then you expected. Everyone shows their opinion on the forums to what's too strong and what seems weak.
Sam looks into each spell described by the players as weak/strong and then decides the best course of action. A patch for spell updates is added and now everyone feels in line with each other in battle, some nice even fights break out and the more skilled(if you can be skilled in mir) players end up victorious and the losers admit it was a nice balanced fight(or more likely cry cause they lost saying the other guild cheats)
I do feel there is more benefit in all spells being accessible then being rare and some people never seeing them. But from the poll it looks like it doesn't matter what I think
The team could always run a second server for the ones who actually want it(fresh start). But then that's also a stupid idea cause then the user count would be half on 1 server half on another :/