A block isn't wasted just because nobody attacked it. It's doing its job: Ensuring whoever's under it doesn't get hit. In fact, a block that deters someone from even trying is doing its job better than a block that is getting pummeled.
Speaking of teamplay, most groups have some kind of tank, someone who's set up to be able to withstand attacks better than the rest of the group. If the block is shielding one of the more fragile members (like, say, the wizard), in favor of the tank, then it works out.
And don't forget to factor in shielding your team and duration.
No it isn't. A block that takes an attack before it fizzles is much more affective than a block that stands there and does nothing. Because it took a turn to put up. A whole action wasted while the other side loses nothing.
Let's take a sample battle here.
4 v 4. 1 Wizard, 1 WC Vampire, 1 Vanilla Mortal, 1 Werewolf.
Team 1 Wizard puts up a powerful block defending himself.
Team 2 Wizard Aims a powerful spell at Team 1's Vanilla Mortal.
Team 1 is down a person.
Team 1 WCV attacks Team 2 Wizard and takes him out.
Team 2 WCV and Team 2 Vanilla Mortal Team up on Team 1 Wizard and deal with him before he can manage another spell because WCV's own Wizards because the block doesn't defend against mental attacks.
Team 1 and Team 2 Werewolves handle eachother.
End of Round 1, Team 1 has 1 Shapeshifter and 1 WCV verse a Vanilla Mortal, a WCV and a shapeshifter. Who wins?
Hint, the team that didn't mess around with a block.
Next Scenario.
Instead of a global Block Wizard 1 Blocks off Wizard 2 from doing anything but leaves himself open. It's a net Zero result.
Wizards are better served being blasty cannons than making evocation blocks because they have the highest accuracy and the most damage. Sacrificing even 1 turn of that can doom the party.
As for the uninvested shield. That's her fault for not spending the time to make it worthwhile. a 1 slot enchanted item isn't super reliable for defense purposes.