Do people in this game not comprehend the concept of shield healers?

[Eien713]

There is always another attack coming in the next 30s, or the heal could have safely been delayed 5s~10s so that the shield would last until the next attack, or it doesn't matter.

Not really. I've been in many encounters where after the raid-wide aoe, the party members take no damage for the next 30 seconds and the shields fall off. Also, is it useless then to pre-shield a tank about to get hit by a tankbuster? While doing Alphascape 3, I've seen the tank get deleted by the tankbuster more often than not because they didn't mitigate and the shield healer didn't shield. Granted, the main issue is the tank not mitigating, but in such cases, the shields would've prevented their death.

This is an ironic statement because you are advocating for overhealing by insisting that shield healers precast their shields.

It's not ironic since the person I quoted was talking about WHM and their excessive use of Medica II, Assize, and the lilies all together.