One: Scholars have to do the exact same
Two: While Bio, Bio II and Shadowflare technically cannot miss, Ruin, Ruin II, Aero (if cross classed) and Energy Drain still can
Three: If you're healing for 2000, it's either: You crit or you're using Cure II. If the party member only needed 1000 healing a Cure would have sufficed. You're just stating a poor choice of spell here.
One: If regen is applied before going into Cleric's stance, White Mages can technically do the same. Although not as potent. Stoneskin is unaffected by Cleric's Stance, however. Lustrate doesn't come for free either and is not unlimited in it's uses.
Two: Energy Drain, Ruin, Ruin II and Aero (if cross classed) do require accuracy. Energy Drain being the most painful one to miss: Not only will you miss out on damage but 266 MP as well.
Three: This exaggeration is way out of bounds. Also: Why would you choose to use Adloquium on someone with no real purpose? If you were indeed to heal someone for 2000 HP with Adloquium, if that shield is not used then it's just as wasteful as overhealing.
Four: Lustrate heals for more over time, that much is true.
The power to soak up MP isn't much of a reason. MP should never be an issue in a competent party or with competent healers. Be it on White Mage or Scholar
The "haste" you're mentioning would be a 30 second 30% skill- or spell speed increase. Haste is something completely different. Actual results may differ from encounter and it's not a gigantic boost when it comes to damage. The only class who majorly benefits from this would be Black Mage. Summoner's hardly benefit from it and TP-reliant classes drain their TP slightly quicker: Resulting in that the bard needs to use Paeon earlier or even more, which effectively lowers the bard damage as well.
Their own "HoT" (Whispering Dawn) isn't always available, especially when the scholar uses Selene over Eos. Neither is as available as having Medica II: It has a 60s cooldown.
White Mages also have access to eye for an eye and so do black mages and summoners. The only difference would be that it has a shorter cooldown time on it, but it's actual effect is not more potent.
The current state of the game isn't actually that imbalanced when it comes to healing. Any content can be solo healed by either healer and the very same content can be healed with two of the same healing classes (see previous posts). But this is about the current state. If the game mechanics remain the same as it is now and we simply get some additional skills and/or minor tweaks. Then yes, White Mages would be at a disadvantage. But not because protect is being tweaked. It's the other classes getting skills to patch up their weak areas whereas White Mage is getting new abilities which will suffer from the issues as it has now.
inb4 the spell actually requires to hit before it heals (which is probably the worst case scenario for this ability/spell)