Took Commander Keskin up to 18. Was expecting to hit the mission sparsity point based on everyone's feedback, but hasn't happened yet. I haven't even been doing missions my own level yet - staying pretty consistently 1 level below me. I've even run into a new series of level 16 missions I'm in the process of chasing down. Maybe the fact that I naturally lean toward exploring the environment is making the difference for me. Whatever the cause, missions mission everywhere.
I've heard people complain of grind-required gaps at 17, 20, 24/25, 30, and around 35/37. Have guys cruising to 19 with just the westside content, so I've dismissed the 17 gap as a myth thrown out by sloppy players. Since I'm leveling my whole stable up together, I'm guessing the new lvl 18 Millennium City content + Blood Moon content will make any old lvl 20-25 gaps invisible to me. So, if there are gaps, I doubt I'll see them till my stable hits 30 - provided they haven't corrected that by the time I get my 8 up that far.