At level 50, a WHM primarily uses GCD heals. And Lily heals were introduced to avoid the opportunity cost of GCD heals.
So again, using Lily heals would still have an opportunity cost where you lose DPS to heal. While you can choose to accept that cost, it remains an opportunity cost. Optimal DPS, which is the end all be all in FF, would mean using Lilies for direct damage. If you can't fit those proposed spells, you aren't performing your "job" according to the FF meta.
To get optimal DPS, you'd use Lily heals as little as possible and rely on your co-healer to keep everyone alive. This results in the WHM hardly healing at all, except for using Assize on cooldown (which often results in wasted heals since, unlike Lilies, it lacks flexibility in usage). Your only significant healing would come from longer cooldown OGCD abilities. These longer cooldown abilities are Asylum (90s cooldown) and Liturgy of the Bell (180s cooldown) for AoE healing, and Benediction (180s cooldown), Tetragrammaton (60s cooldown), and Divine Benison (30s cooldown) for single-target healing. Without Lily heals, WHM has very little OGCD AoE healing, which is only sufficient in fights with significant healing support from co-healers or tanks, or when incoming damage is trivial. These latter two are what people are trying to address in this thread.
Even with Lily heals, WHM has the lowest HPS in recent healing statistics on FFLogs for savage content. It doesn't need any further healing nerfs.
If you still disagree, please explain how these issues could be avoided. Do you believe the existing OGCD AoE heals are sufficient for a healer's kit? Asylum is a weak HoT, and Liturgy has a 3 minute cooldown. Without Lilies, you can't use Plenary Indulgence on OGCD heals, reducing AoE healing even further to a level far below what a WAR can do. Or do you think the FF community will stop demanding every last point of damage from players? If so, you'll need a far bigger plan than just a few spell additions.