Really interested in Sekiro, but I'm not a particularly skilled player.
I can get through most of the non-DLC stuff in Dark Souls 1 without trouble, though I did have the benefit of coming to that late and watching a lot of people play it before I tried for myself. The DLC stuff was hard. Artorias nearly broke me, but I was able to beat him after a lot of tries. I did not much care for Dark Souls 2. The life reducing mechanic was very punishing and I had to invite players to beat a couple bosses. Did not play Dark Souls 3.
I platinumed Bloodborne as a solo player, but only by grinding a lot and maxing almost every stat to the soft cap, which actually makes a pretty noticeable difference in that game. I was pretty happy with the level of difficulty in Bloodborne.
Seems like people are saying Sekiro is harder than Bloorborne. Can anyone confirm that to be the case?