If people want to use a strategy that loses more often than it wins, that's perfectly fine with me.
There is a legitimate use for parafusion though, it can be used as a method of stall to beat things that would normally wall you, yet can't kill you particularly quickly. Here the reliability doesn't matter so much since, on average, you will kill them before they kill you.
Moral of the story:
using paraflinch jirachi to try to beat a heatran = bad
using paraflinch jirachi to try to beat a recovering wall who you can't 2hko who can't 2hko you = good
There is a legitimate use for parafusion though, it can be used as a method of stall to beat things that would normally wall you, yet can't kill you particularly quickly. Here the reliability doesn't matter so much since, on average, you will kill them before they kill you.
Moral of the story:
using paraflinch jirachi to try to beat a heatran = bad
using paraflinch jirachi to try to beat a recovering wall who you can't 2hko who can't 2hko you = good