pros and cons

pros

more referees mean more officials to complain to, if the main ref won't listen, you have 4 more guys to annoy and even the 4th official if that doesn't work.
More referees mean also more targets to throw stuff at, now wherever you sit you will have your own official to abuse, the guy in this match got a lighter against his head when he didn't call a corner shot.
More referees see more. Maybe so, but all these Portuguese refs didn't see how Standard scored from an off-side situation.

cons

It's off-side!
What?
It's off-side!
No I don't think so, and you Jorge what do you think?
What?
Was it off-side, what did you see?
I don't know, let's ask Joao!
What? Sorry I was just picking up this lighter.
Well I say it was off-side!
No it wasn't. Don't listen to him he had it wrong the last time!
What?
And this assistant, the one who was hit with the lighter, was just walking away, facing the corner flag when a fight broke out between two Standard players and the HSV goalie. He missed it!. This is the very reason why he is there, why he got a plane ticket, a hotel room, briefings, dinner with the VIPs etc
And think of the poor guy who has to stand in the box of the team that is attacking all the time, 75 metres away. He just stands there, in the cold, not allowed to talk to the goalkeeper.
It probably only works if you train them especially for this task. I wonder who wants to be an extra assistant.

Proenca

There was some bad blood in the second half, HSV were stalling a lot, Standard players were irritated and fouled a lot, coaches arguing with the 4th official and had to be restrained, some idiot was annoying players with a laser. Every one seemed in a foul mood. Proenca is not the man to calm things down. But he is not a bad referee.