Kasper,
Here's the point you are missing...DFT is a theory, not just a program. The 5x5 is also based on dual factor theory. I think you should use DFT all the time because it is the correct theory as to how to get bigger and stronger through weight training. Supercompensation is just wrong.
So do I think you should use DFT when cutting? Yes. When bulking? Yes. When training for hypertrophy? yes. When training for strength? Yes.
There is no need to change anything from a bulking plan to a cutting plan, except the amount and kind of food you stuff down your face. Regardless of the plan, you are still lifting against the backdrop of DFT.
Hope that makes sense. The exercise selection, sets, reps, etc. may change based on your current goals, but the theory behind it does not.
As for failure, guys get lost in what JS and Gavin and others meant when we said failure isn't needed. The fact is, when training for strength, I fail all the time. I squat 750, then throw on 800 and dump it on the pins. If I'm doing 5x5 I may only get 3 or 4 reps of my last set. That's not what we meant when we said failure is bad. What we meant is that "total muscular failure" is bad - i.e. - this idea of using the weider principles to beat your muscles into submission; drop sets, cheat reps, negatives, help from spotters for 4 reps after you fail,etc. Some of those HIT guys keep stripping weight off the bar until they can't even pick up the bar. Their muscles are unbelievable beat. There's no way to recover from that type of training enough to train the same muscle groups 72 hours later.
So if it says to do a weight for 5x5, then pick a weight that is really tough to get all 25 reps with. If you get them all, bump the weight up the next week. If you don't, that's ok, keep the weight the same and try again next week. It's really not all that complicated.
Matt