I think it's stupid that you don't get credit at all if you aren't there for the whole fate. Just now my fate, 'breaking dawn', popped. I didn't know where the fate was but was in the area and kept checking my map to look for it. When it popped I hightailed it. It wasn't far at all (took me roughly 20 seconds) and it was at 0%. I arrive only to discover some asshole healer and his chocobo was already close to killing it. I managed to toss in a few shots (thunder 3 and Fire 3, followed with a few fires) but I didn't receive any credit and that healer just happily jumped up and down before teleporting away. I was so pissed off. If they're gonna force us into doing fates they should at least give us credit, especially those arriving just a few seconds late.