Should probably mention where Softcore took me ~10 hours to beat on Elite (skipping unneeded side quests), it took me roughly 45-50 on Hardcore, where a lot of time was spent changing between three friends groups and clearing the same thing over and over.
I was an Outlander and went very heavily into the Lore Skills tree, where I tried to max Tangling Shot, Glaive Sweep, Bramble Wall, Burning Leep and Dodge Mastery while also trying to max out Stone Pact and Shadowmantle in Sigil Skills. I ended up killing the last boss at level 52 or 53.
(Sorry for the late answer, I went to the dog park.) I also want to point out, it was challenging to beat Elite on Hardcore, though I personally believe that Inferno on Hardcore in Diablo 3 is more challenging.