That "youtuber" is a dumbass and you shouldn't take his advice.
For new players, merging Diablopterux is the only thing they can do to have an extra weapon for all grids instead of getting a SR for each grid to fill up a slot. It's easy stats too. We should get the last copy on a next update that gives more missions, (as well as a SSR non-hime weapon ticket.) Once it's use is up, which could take up to a year for newcomers, it's a useful fodder :shrug: