10-15 reps at 80%... Obviously great for hypertrophy (especially when you are strong enough to use big weights) and that's why bodybuilders become rep-strong. In powerlifting however, sets of 5-6 at 80% is more the mark -- My current DL 5RM is about 85% of my 1 RM and it is likely to become more like 80% when I stall on rep work and begin to train on triples, doubles and singles. I haven't reached that point yet.
Right now, I am into my second year of training and gaining at 5-8 reps on most lifts; DL are an exception -- whenever I put 365 or 355 on the bar and take the set to 6+ reps, I get some minor strains, a sore lower back and so on, but I hardly get sore when doing like 385 x 4 (this is about 85-87% of my max), probably because I'm able to maintain good form and conclude the set before my core gets too loose. Some poeple may gain deadlifting in the 8-10 rep-zone, but I am not one of them. Eventually I will get so strong that even a max set of 4-5 may become too taxing (unless done infrequently), at which point I will do some flip-flopping (like doing 5 x 3 or 6 x 2 with the same weight I could handle for 5). But this is deadlifting and this lift is quite special (and it is my favorite one!).
I have found it easier to focus on just one goal; mine is strength. My main concern is getting that extra rep so I can put more iron on the bar when I hit 8 reps (5 for DL). The weight increase depends on the lift. I use about 5% for Bench and Squat; on Squat, going from 270 to 285 to 300 proved more effective than adding only 5 or 10 pounds. On other lifts, adding 10 lbs is the norm for me. A susbstantial - but still manageable -- increase seems to work best for me; and I don't mind to work hard. I typically conclude the set one rep shy of failure.
Thankfully, hypertrophy may come even when you don't prioritize it: my arms are now 17.3" and this is exactly 10 inches more than my wrist (so I don't expect them to get much larger; maybe they'll creep up to 17.7 or something...) and they are in line with my back, chest, thighs, so forth... This size comes from heavy lifting for relatively low reps (well, bodybuilding low, but powerlifting high-ish) and a focus on strength. I seem to put slabs of muscle by doing what a lot of powerlifters do when they start out. In fact, it works so well for powerlifters that I am not big by any means in their crowd! (I am 6'1" 238 lbs [not fat, but NOT shredded
], which is about 25 lbs lighter than Mike Tuchscherer, who is also 6'1" and is known to compete in drug-tested meets)