@Selly, I can agree, that Freed has taught Laxus this one spell and because they were team for many years and Laxus was observing Freed, he was able to learn it without much problem. But you sound like Freed has written this spell in Magnolia and then miraculously teleported it to Laxus' place and that's something, I can't agree with. At least until Mashima confirms it, but for now any single panel in manga indicated, that it was Freed who wrote this runes. One important thing, I don't know on which translation are you basing, but in raws Laxus said: 'No one can break your jutsu shiki so easily", so he's not talking about Freed's one spell, but his magic as all.
During Fantasia Levy needed tones of books to re-write Freed's jutsu-shiki, because it was new magic for her. During S-class exam it was easier for her because she already knew this kind of magic. And Freed never said it was easy spell, only there was some time needed until it disappeared.
I can really understand, that Freed is underrated character in FT, I also like him very much and I wish he was more relevant to the plot, but let's not exaggerate, he has his role to play and I'm pretty sure he will show up again in the near future