Of course the Ravines of Time are too powerful to be used. Well it's too difficult to mass-produce the effect of the Eclipse Gate anyway. Unless Hiro writes that many opened up around Earthland. Arguably almost all the Alvarez Arc with the Spriggan 12, Fairy Heart, Acnologia being a Magic Dragon, the Ravines of Time etc are easy to abuse and overpowering. Also I do understand that unlike other common fanon wikia, like DBZ, One Piece, Bleach, Naruto etc. Fairy Tail is rather almost set with its power levels. I mean for a long time, it was thought Markarov and Hades were the strongest we could see for a Mage. Now we see Mages on the level of City-Busters like Ajeel or Invel, to Nation Crushers like Irene and August and for Fairy Tail that is God-Level Magic. But they are rare and story-plots. Most Mages in Fairy Tail don't even reach low Saint level.
Also I understand that Slayers and especially Dragon Slayers are easy to abuse. On other fanon I'm not too fond of this many rules, but that is because there is a lot of room for highest level characters on my other fanon. On Fairy Tail, most Mages aren't the best fighters or even very powerful. So it's understandable that most story-exclusive Magic and events can't be mass produced as well as there are not like a 1,000 Acnologia clones everywhere.