It's not about making him suck--it's about making him psychologically incapable of jumping, incapable of taking the jump in the first place, not incapable of making it once he does jump.
A failed athletics roll for a jump can just as easily be not jumping in the last second as it can be failing to jump to the other side.
Doing it the way you suggest basically makes a whole lot of blocks useless, because anyone can break just about any block with their apex skill.
If breaking the block like that makes sense, then yes, you can. But using your apex skill is not always appropriate. Incite something in a social setting, and you can't just use fists to get out of it, without making a scene.
You could, certainly. I just feel that it makes blocks a lot less useful if they can be easily beaten by any skill, despite it not making sense.
Granted, blocks are my least favorite mechanic in the DFRPG. But that aside, I feel that they become way too powerful if you can force someone to do something to overcome it. That's basically a grapple. And I have no problem with modeling something like this as a grapple, but then it should follow the grapple rules and require an appropriate aspect before initiating it.
Another problem I have with your example is that I can't really see it being used in a game like that. If you have a conflict and you block the other character from jumping over to you, then it's basically game over, you won. But that's a taken out result and should be a taken out result in my opinion. You can, as I said, reach that by attacking with incite emotion and taking the other guy out, but not with a block. What you can do is increase the zone border for your opponent. That's a block action right there. But he is still able to jump. He might have lost some of his confidence in his jumping abilities, but those abilities are so awesome, that he can still succeed. If both characters have the same skill level, then the chances are even. If the vampire has a lower skill level, then yes, he has less chance to keep the block up.
Or you have a chase scene that you model as a contest. In a contest, you don't have blocks at all, but I could easily see using incite emotion to get some points and justifying it by saying you temporarily make your opponent afraid of heights.
Two things: One, this makes a veil next to useless as a unique block; two, this is directly contradictory to how veils are described in the rulebook. It's a block against perception, and swinging your fists or sword around isn't a perception roll. The rulebook outright says that it's a special type of block that does not directly oppose damage, but lets the caster avoid being attacked entirely.
Looking at Molly's stats vs. the Gruffs at the start of Small Favor, her rote veil, 3 shifts, would be totally pointless played that way--the Gruffs have exactly the same chance of hitting Molly under a veil as they do hitting Molly when she's just standing there in plain sight. Something with a Superb attack rating has a 93 percent chance of hitting Molly when he, theoretically, cannot see her, hear her, smell her, and has no clue where she could be in the immediate area. Does that seem right to you?
With a veil up, you can easily justify your opponent attacking someone else. Maybe by paying a fate point, maybe just by pointing it out to the GM. Remember that Molly not only used her veil, but she used her Good Deceit skill, too, when she misled the Gruffs into thinking she went somewhere else. She might even have used her Great Discipline to "keep her cool" or something like it.
Then again, looking at OW, the gruffs are not really a threat to Molly. By that writeup, they have Fists at +3 (QW45 but they use the Goblin sheet OW43), which is a match. Now let Molly do an overcharged version of her veil instead of the rote (and since she has to cover her siblings as well, that's likely the case), and she can easily use it to get out of the way. Throw in a Fate point, and you are good to go.
If you are fighting something with a superb skill and your own skills are only at good, then yes, you are going to have a bad time. You can make up for that by being way clever and using your better skills against your opponents worse skills with maneuvers, but a veil does not make you invincible, it is just one way to avoid the worst of being hit. Otherwise a veil with some specialization is an automatic "I win" spell.