Non pre-cook lasagne does not necessarily live up to its promise of saving you trouble. Cooked from raw, it can absorb a good deal of sauce, leaving you with a dry wodge in the oven dish; if bits of the pasta are uncovered by sauce, they remain brittle.
You can ensure more even cooking by blanching the sheets for a minute. But you have to do so in small batches, because otherwise the sheets stick together, as if superglued. Pouring boiling water on to a batch of sheets, as Yotam Ottolenghi once advised (see this entry), is asking for trouble.
However, you can soak all the sheets you need in cold water. After 5 to 10 minutes, they should be floppy. If they look as if they’re sticking, they can be peeled apart (because you don’t have to put your hands in scalding water); but I have found that they do not stick hard. You’ve saved yourself the trouble of boiling the pasta and laying out the sheets separately; and you have ensured that it will cook evenly.
Having said this, I should add that this kind of lasagne is not as nice as fresh, or as the dried variety that does require pre-cooking. But in many shops and delis nowadays, it is all that is available.