Generally, a block is intended to create a hindrance to one specific action. A grapple is a special case and, the way it is written, I'd rule that it could only target a single person or creature and would tie up your own action in the process. A long duration block to all actions to an entire zone would indeed be significantly overpowered.
Remember, even the Orbius spell is a block against breathing that could cause someone to suffocate and pass out. Nothing about the spell's description claims that the person under it's effect can't do any other action, like shooting at the caster. Now you could call it a complete physical grapple, but notice that the grapple rules state you need to tag an aspect first to establish the grapple, so the spell is clearly missing something ... i.e A maneuver creating evocation the previous round.
In the Invoke For Effect/Compel argument, that does indeed look like a compel. I wouldn't allow tagging for that as it's too strong. Now the GM himself could claim that the NPC passed out from his wounds and quietly write down that this NPC has a Fate point to use in the future should he survive.
As for Mental attacks, it is indeed skirting dangerously into 4th law territory due to one simple fact: mental consequences are almost always psychological scars that last a while and generally compel someone into either following specific actions or denying them others. For example, you could blast him with a mind-crushing wave of fear. If they survive, they could get stuck with moderate or severe consequence of The Bogeyman Is Real And He Is After Me, and hence be naturally paranoid and constantly looking over his shoulders. You could try to narrate it with your GM that you are casting a sleep spell who's effects only last the scene and should not inflict any consequences, but even there it's a hard sell.
Although in the latter case, you could cast it as a maneuver, defended by Endurance, that afflicts someone with the Sleepy aspect as a *physical* effect rather than a mental one.
