I've been using some variations of the combos in the OP. Specifically, the first intermediate ground combo, instead of going 236D > RC > dash > 2C, I substitute it with 236D > RC > 5DD > 6DD > etc. Also, the first advance anti-air, I make the same substitution after 214D > RC > land > dash > 6C. Instead, it's 214D > RC > land > 5DD > 6DD > etc. In both cases, the end result is somewhere around 500 less damage at the end of the combo, but I can hit those nearly 100% of the time, whereas if I try the combos listed, it drops to around 50%. I figure it averages out that I do far more damage with doing the less complex, lower damage version just from consistency.
I've also noticed in training that the timing for the end of the combo gets much tighter when you're adding more hits in and the opponent has more chances to tech (ie, the higher damage versions listed here force you to be much more precise with the j.DD, dj.DD, 214D ender than if you use my simplified versions). For those of you having problems hitting these combos consistently in matches, you might want to try the substitutions until you feel confident in your execution.
