I can totally see OPs point as a valid point, for a couple reasons.
If you're leveling, a lot of people like running dungeons for the XP. If you're sitting in a long queue, you can do Fates for extra XP. However, you cannot have a choco out while queueing. You cannot be in a "Fate party" (which would normally have a healer, though not always) while queuing. So, you're forced to have no self heal at all while doing Fates (in these situations) or you're forced to sit around AFK while waiting for the half hour DF queue. Either way, MCH is the only class with absolutely no access to a self heal.
Not to mention, in PVP. You're, again, the only class who has no access to a self heal. While this is not game breaking/changing, I totally feel for machinists on this one.