Aside from this awesome forum, Ferrite doesn't have a groove based timeline, but imho it's the best clip editor in IOS. (convenient sample accurate editing is a must-have for me) It can handle very long files, but doesn't feature fx-busses like typical DAWs. The absence of a beat timeline can be circumvented by importing some (long) dummy beat as your ruler. You may check the basic editing features with the free version - if you get along with it, I can make a test with a 1 hour file to check it's performance.