Ask your Storyteller
The book offers no answers, here is mine
Sadly, there is only one book mentioning this ritual, and its description isn't very specific.
However, VtM is not D&D. It is not supposed to be just played as the rules say unless the GM has a reason to object, and the whole WoD actually requires a lot of work on Storyteller's behalf. By design.
As I read that, the participants can benefit from their Willpower, the temporary pool or the permanent value, and the main benefit is the ability to arm the roaming participants better without risking the actual holder of high Willpower or those who generate a lot of it.
Sharing the temporary pool means that the participants can spend their Willpower pool on each other's behalf, for example, for the purpose of obtaining automatic successes for particularly dangerous rituals and Paths: the ritual itself is rather harmless and easy to perform. Is it powerful? Damn yes: when you roll Willpower for the level 5 Path powers, each die is only worth 0.2 successes on average, and there is a good chance to botch the roll), while just one point of Willpower spent effectively adds 5 dice to the pool and guarantees success. Such a way to use Willpower is actually a huge power by design, but uses a very limited resource: recovering Willpower pool isn't easy. Splitting the load is a huge advantage. For example, someone knowing a powerful combat Path could invoke chaos with loads of Willpower available in this way.
Sharing permanent Willpower means that when a participant of the ritual has to roll their Willpower, they can roll the highest one available in the circle. For example, the roaming participant with Blood Boil can benefit from a circle where someone has a Willpower score of 10 and deliver a rather stable average of 3 health levels of aggravated damage per turn, or even 4, if they have the True Love merit. There are ways to boost your Willpower even further, but that's not the point.
I definitely think that Willpower values can't be added together: you have to use one value or another, otherwise, it would be possible to achieve enormous values if you had a good amount of participants. I also definitely think that this doesn't allow you to spend more than 1 Willpower point per round.
About your point
You say that you don't like that reading, and that's OK. As a Storyteller, you can exclude this ritual from the game universe, change the way it works, read it as you want, etc. But the way it is written doesn't leave much ground for any other readings, so by interpreting it in any other way you are probably actually changing the rules.
In any case, note that Thaumaturgy is supposed to be powerful. There are reasons for it to be a trademark, a secret of the Tremere clan. Why guard it if it has no use? Don't overnerf it.