I'm playing a monk in the Adventurers League. All the way up from Level 1, and he's currently level 10.
He's a human variant, so dex = wis = 16 at level 1, ergo AC 16. But I went with Defensive Duelist rather than Mobility, and have been pretty happy with the choice. Essentially he was AC 18 vs. melee attacks from level 1, as he could parry melee attacks that only hit AC 16 or 17. (Technically only 1x/round, but I don't think it ever happened that that mattered.) Saved his bacon more than once.
In the long run, this feat shores up one of the monk's main weaknesses (Melee AC) as monks later get deflect missiles, and proficiency in all saves. Now that he's level 10, he's actually pretty tanky, and can fend off attacks better than many of the folks in plate mail.