Around 5 hours 20 minutes to clear all the DLC battles, as shown, in this unedited playthrough. I only edited out start up screens and OBS recording menus since this was done in a few gameplay sessions. Very good DLC. I believe 4 of the 5 courses are optional but I completed them all. I reloaded a previous save to resume these, as I had the option to play through them before the final boss, for better gear, but wanted to seperate the playthroughs, so did it later.
There is alot more enemies and the battles are longer than most of the ones in the campaign , so there was definately more save reloading but nothing insane. It got tense near the end of some of the matches, fighting off alot of enemies with 1 or 2 party members remaining. These are more like challenge trials, but you get some decent weapons for the main campaign, if you decide to do them prior to the final stage. I felt pretty overpowered so it wasnt needed, but its a cool free bonus.