The combo you're doing does more damage with the command grab ender. But my execution for command grabs mid combo is garbage so I don't do them myself.
I think he's unpopular because he's kind of bad. Maybe its just me crying about my main but floaty jump, slow walk speed, slow dash speed even when MBed, no reversal, gaps in his strings(getting hit by a MB back 3 mid string feels absolutely terrible), not great mixups, and from what I can tell basically no way around zoners at all, I don't see what makes him stand up to characters like Black Adam, Deadshot, Superman, Supergirl etc. I tend to rely too much on MB back 3/forward 3 for all my options.