I think I treated it as a cutting exercise as opposed to a strength gaining exercise.... and that made me hate them...... that may be my fault, but as far as developing my core and helping cut lower body fat on a calorie restrictive diet...... it worked....but I would be wiped afterwards.... to the point that whenever I did deadlifts at the end of my workout, I would always either cheat the weight, or reps.... and not get the full benefit..... and by doing that, I saw bodyfat reduction to a point, but not strength gains....
Yeah the conventional deadlift should be performed as "strength" exercise. This is just my opinion, but I think it's always best to do them with very intense loads. Reps aren't the end all be all with deadlifts in my opinion.
If you can hit the 3-5 range, you're good money.
Heavy triples, heavy doubles, even singles, they're phenomenal. I usually always squat before I do them because if you do deadlifts first they'll murder the stabilizers that you want strong when you squat. Same reason why at powerlifting meets they always squat or bench
before they deadlift, and it's also why most people don't reccomend you isolate your core on the day before your deadlift or squat sessions.
I always performed them without a belt so it definitely helped train with breathing and tightening my core on the initial pull
I can't link one source bro, this is just the result of tons and tons of random reading, YouTube watching, forum reading, anecdotal shyt. 
