It is my understanding that the goal of hypertrophy training is to maximize time under tension to stimulate muscle growth. However, most heavy compound movements such as deadlift seem to do the opposite as they can only be performed for few reps. For example, the push-pull-legs routine I'm currently following contains 1 set of deadlift at 80% of 1 rep max. This sounds more like a strength/powerlifting training. Is there some real advantage of including these big lifts in hypertrophy program?
See my answer to a previous question, which also answers your question: Confusion about reps vs time under tension: aren't these two things contradictory?
In short, the idea of long times under tension being important is nonsense, made up by Charles Poliquin. You can achieve hypertrophy over a huge range of relative loadings, as long as you're working similarly close to failure. 80% of 1RM isn't even close to being too heavy to be useful for hypertrophy. It's really only at 90+% of 1RM that you're getting to the point where you're practicing maximal strength more than you are working on hypertrophy.
The most important for hypertrophy is to train close enough to failure. "Time under tension" is not the driver of hypertrophy, but it is doing the exercise close to failure that is the main reason for muscle growth. For now I won't go into the details of the different types of hypertrophy and different types of "failure", it is enough to say that, as you get closer to your max number of reps, more and more muscle fibers get activated, and therefore stimulated for growth. In this sense, it is not so important how much total time was spent "under tension" because in the beginning reps, only some share of the muscle fibers are actually activated.
All this means, that there is a wide rep range that is effective for hypertrophy, as long as you get close to failure. The rep range is usually given between 5-30 reps. Most common is around 10-12 reps or less, because more than that becomes quite painful and is not more efficient for muscle growth. In any case, it is possible for an exercise to effectively induce building muscle with 5 reps, or 10 reps, or 20 reps, it is really a matter of personal preference.
"Close to failure" usually means no more, than 1-2 reps in reserve. So no need to go to actual failure every time. However, from time to time, it might be useful to go to actual failure to get a feeling of where you are.
Assuming your 80% of 1rm is roughly accurate, I would assume you can do a bit more than 5 reps, let's say your max at 80% 1rm is 8 reps. So I would either try to do at least 6-7 reps with 80%, or stay with 5 reps but increase the intensity to 85%. The reason why people don't often do 10+ reps of compound exercises like deadlifts for hypertrophy, is because with lots of reps it becomes very challenging for cardio, so you might actually have to stop way before muscular failure because you're out of breath. On the other hand, for isolation exercises eg. a barbell curl, people usually do more reps for hypertrophy eg. 10-20, because with few reps technique is more likely to break down before muscular failure.
In any case, I think the most important "skill" to have for hypertrophy is to be able to accurately judge the number of reps in reserve. One way is, as already mentioned, occasionally doing your set to actual failure, if you can do it safely, and try to remember how the last 1-2 reps felt. I usually avoid that though to reduce risk of injury. Another way is to film yourself and analyze the rep speed. Once the time you need to complete a rep starts to increase significantly, you know you are close to failure.
Another important consideration is volume. It is usually recommended to do at least 10 sets per week per muscle group, all of them close to failure, to induce hypertrophy. So the rest of your program should be designed to have enough sets to cover each body part enough times.