So your argument is that Lustrate and Cure 2 are the same skills in terms of usage, in that you use one when you need an instant heal while in Cleric stance, and the other you don't?
And I think the best comparable to Cure 2 for Scholars isn't Lustrate, but Adlo. Yes, I'm aware that Cure 2 has no shield component, and Adlo has no cost reduction proc, but when do you cast Adlo on somebody? When they are missing HP and you anticipate them taking damage soon - otherwise the shield is wasted. When do you cast Cure 2 on somebody? When they are missing HP and you anticipate them taking damage soon* - otherwise you'd cast a Cure or a Regen or just let the SCH fairy take care of it instead. In both cases, this can be a tank or a DPS or a healer, whereas Lustrate performs much worse than Cure 2 or Adlo on DPS or healers. Admittedly the amount of HP missing before the spell becomes useful is different between the two, but the strength of both spells relative to HP pools (and the cost of both spells relative to MP pools) is similar. Also, both Cure 2 and Adlo work only while stationary or swiftcasted, both are affected by healing buffs/debuffs, and both require a cast time to work (again unless swiftcasted). Conversely, Lustrate is usable on the move, couldn't care less if Twintania stacked Death Sentences left and right, and happens right now.
I do agree that Bene and Lustrate are two different abilities and directly comparing them is weird. I just don't think that Cure 2 and Lustrate are the same skills in terms of usage. Yes, you should try and minimize your casts of both, and you might use them roughly the same number of times in a minute, but the way you use them is actually different.
*Or if you have a Freecure proc, but that's a reversal of the norm - a free Cure 2 is more efficient than a Cure is more efficient than a normal Cure 2.