I'm levelilng MCH right now, and this bugs me. Compared to levelling the healers and PLD, I don't get a whole lot of feedback on if I'm doing it correctly. It turned out when I was working on BRD that I was doing it very wrong at 50, which I found out later after I failed an instance, made some changes, did it again, and did double the DPS of the previous run through (unsurprisingly, we cleared that one). I only knew there was a problem and that I'd improved on it because ACT told me so. The game told me absolutely nothing. It will also be telling me nothing when new abilities show up that drastically change what I should be doing (which isn't a thing that really happens to healers in the same way).

I don't find the obfuscation helpful to trying to play DPS given how much more complicated the job mechanics are compared to the healers I've been playing. God help me if I got to 70, totally failed an Ex Primal due to my lousy DPS and only learned about it at that point (which is a thing I've also seen happen to people in my FC, it was very discouraging for them). As you said, the tanks and healers don't suffer the same shock. Bardam's Mettle gives them a great indication of what's going to be expected when someone shows up undergeared, without cooldown usage, and gets utterly destroyed. DPS do not get the same treatment in there. If stuff takes longer, it just puts more stress on the healer.

I don't really view lack of feedback as a good thing until it suddenly shows up and gets you kicked out of groups.