Found it!
"Q: There are a lot of battles that require the memorization of patterns in order to win, but in the future will there be any battles with more random elements?"
"A: We’ve been receiving questions about this even here at the Full Active Time Event in NAGOYA, but we don't have any plans to implement something like this. For really close end-game battles, in particular, random elements would make these encounters very luck-based. To give an extreme example, in one phase of Titan extreme there are four abilities he uses, and if you remember the pattern, it’s easy. However, if every time the pattern changes, or the number of times he uses a certain ability is different, what’s going to happen then? It’s really not difficult for us to do, but it would make it difficult for us to do anything about game balance. Another example is of two free companies racing to beat the Second Coil of Bahamut turn 4. While one group easily cleared it because nothing but easy abilities were used in succession, the other group ate nothing but the worst of the abilities and was unable to beat it. I believe it would become extremely frustrating due to a feeling of unfairness. However, there are some random elements in content already such as what party member is going to be targeted by an ability or which enemy is going to use an ability.
But as they as say, “experience is everything,” and since we’ve received a lot of feedback on this, one of the three new dungeons will have a boss that has a high degree of randomness. Everyone’s average item level is quite high so if you really push it you’ll probably be able to get past it, but we’d like you to challenge it without pushing it too hard and hear your feedback. Our policy isn’t such that we definitely won’t add random elements, but we want to create battles that offer players a fair chance of clearing.
Also, we haven’t announced this yet, but we’re thinking to try something else new in patch 2.3. We’re considering preparing a ridiculously high difficulty encounter where the reward would only be a title. This would be at a level that the development team might not even be able to beat, and we’re interested to see what kind of players will rise to the challenge. We’re preparing “Something-Something Extreme,” but it may not be ready in time. The rewards will be the same that you would normally receive, except for the special title."
Letter from the Producer Live Part XIV 6/04/2014