Only for specific strategies
Resource cost to you: 4 mana + 1 fast action + 1 zone (exclusive) +1 spell point
Resource cost for opponent: 2 mana per enchantment destroyed via Dispel. Seeking Dispel, Purge Magic, Destroy Magic, any other?
There is no surprise "foil your plan" one-use benefit like with revealing Armor Ward.
Then there is the undefinable resource trade-off between you and opponent in ensuring it is not destroyed.
So Wardstones work great in a build with lots of "must dispel" enchantments These tend to be Direct Damage or Mobility enchantments that can target enemy mage like Ghoul Rot, Magebane, Poisoned Blood, Force Hold and Force Crush (from FvW). Because they add a clock and bad things happen if not removed. Obviously transferring negative enchantments in 1 free action via Transfusion when enemy is within range 2 (Enchanter's Ring bonus as you stack them hidden on yourself) is the basis of strong fun builds in Warlock, Wizard and Forcemaster.
That's not to say that other enchantments fall in this category depending on situation and synergies. Vampirism for tempo switch, damage barriers vs. swarm or defences vs. big, agony on a multi-striker, there are many other ways to force the opponent to use up his dispels.
So yes, in the right build, Wardstones can be great but they have an investment cost.
German gaming culture means you can deconstruct this game into its mechanics far easier than others (just like Charmyna has). But whilst I did exactly the same as you with preparation theory crafting when I started, the subtleties of the game are not actually apparent without playing, experimenting to improve and iterating your ideas (otherwise known as "trial and error").
Cnoedel, I will reply to your updated Wizard Control build soon (really busy) as it deserves a better response than I have time for now. But it's looking good (there are still a few tiny issues you may encounter with it).