the normal content is too easy

[Lauront]

Because thats the kind of SMN that would waste a GCD on a 200 health heal when they could be doing around 20,000 damage with their spells. I don't think it can even save a tank from an auto attack at this point. But instead of contributing to killing the boss quicker so the party doesn't wipe to a damage check or have to see additional mechanics that could wipe the party they have decided to waste their GCD on something worthless prolonging the encounter instead of adding value.

For a SMN heal to barely save a fight it would mean that the fight would be easily winnable if the SMN actually damaged the boss and killed it faster.

There is such a thing as opportunity cost and efficiency. A RDM heal and a PLD clemency may be a different argument because even though it is preferable for them to DPS there are some scenarios where they can sustain party members long enough to win an encounter. A SMN heal is so inefficient it has no such capability.

There's also the fact that SMN can tap into some decent healing via simply continuing its dps rotation into the phoenix phase. Granted, it may not coincide with when you need it but I think your other points solidify why Physick has no real use case here.