Holes in roof gutter

[Innuendo]

That is a pretty good advertisement for drilling holes.
The fact you still have gutters is proof that they should be there.
That's not to say you haven't made a point. They need to be sealed and painted to avoid moisture entering between panels.

[Len1955]

I think Innuendo is right if you are going to drill holes you need to get it right. The problem with this hole is it's been drilled too close to the roof body. If you look closely at the pic taken from the top you can just see the two folds in the sheet metal coming together & there's a small gap which let water in.