Magic Guard and Aroma Veil are not comparable at all. Both cover totally differents bases.
I'm insanely surprised how I forgot about this, but yeah:
Magic Guard does not protect from Taunt, Encore, Heal Block, etc. Magic Guard only protects from
indirect damage (weather conditions, leech seed, poison, curse, hazards, etc); it does not affect the secondary effects of Status whatsoever. It is also only limited to 4 families lines (Abra, Cleffa, Sigilyph, and Solosis), so whats the point (Despite the fact that all 4 Pokemon lines are completely capable of using their ability)?
So yeah, Clefable and Aromatisse are completely different ability-wise; Cleric Clefable isn't as somewhat viable as it used to be, despite having Heal Bell/Aromatherapy, and a good HP to pass with but Chansey and Blissey completely outclass it now, and because of it, it's better off with just Aromatherapy/Heal Bell, and/or being a self recovering Sp.Attacker with Softboiled.
So what does Aromatisse have that Clefable, nor even the Chansey line have in common?
It can (almost) never be set up bait.
Encore, Taunt, and Torment can
never penetrate because of Aroma Veil, and Aromatisse can just simply hit back at Sableye with Moonblast:
0 SpA Aromatisse Moonblast vs. 252 HP / 252+ SpD Sableye: 192-228 (63.1 - 75%) -- guaranteed 2HKO after Leftovers recovery
Sure, that slow, unbearable speed can be a bit of a problem, especially against Setup Sweepers, but you can just simply lay out a well played Toxic, and get yourself an Prankster user of your own, just to up the ante. An untauntable 203 Max HP Wish + Protect is even worse, since it can self recover just as reliably, albeit, slowly.
Oh, and it can wall Dragon, Dark, and Fighting types just as easily as Clefable can, so I don't see why this thing is the "bottom of the barrel" Fairy Type.
Vs. Machamp:
Clefable:
252+ Atk Machamp Dynamic Punch vs. 252 HP / 252 Def Clefable: 87-102 (22 - 25.8%) -- possible 5HKO after Leftovers recovery
4 SpA Clefable Moonblast vs. 252 HP / 4 SpD Machamp: 224-266 (58.3 - 69.2%) -- guaranteed 2HKO after Leftovers recovery
Aromatisse:
252+ Atk Machamp Dynamic Punch vs. 252 HP / 252 Def Aromatisse: 87-103 (21.4 - 25.3%) -- possible 5HKO after Leftovers recovery.
0 SpA Aromatisse Moonblast vs. 252 HP / 4 SpD Machamp: 234-276 (60.9 - 71.8%) -- guaranteed 2HKO after Leftovers recovery
Vs. Tyrantrum:
Clefable:
252+ Atk Tyrantrum Earthquake vs. 252 HP / 252 Def Clefable: 110-130 (27.9 - 32.9%) -- 86.7% chance to 4HKO after Leftovers recovery
4 SpA Clefable Moonblast vs. 4 HP / 0 SpD Tyrantrum: 302-356 (98.6 - 116.3%) -- 93.8% chance to OHKO
Aromatisse:
252+ Atk Tyrantrum Earthquake vs. 252 HP / 252 Def Aromatisse: 111-131 (27.3 - 32.2%) -- 56.9% chance to 4HKO after Leftovers recovery
0 SpA Aromatisse Moonblast vs. 4 HP / 0 SpD Tyrantrum: 312-368 (101.9 - 120.2%) -- guaranteed OHKO
Vs. Mega Absol:
Clefable:
+2 252+ Atk Mega Absol Night Slash vs. 252 HP / 252 Def Clefable: 135-159 (34.2 - 40.3%) -- 42.5% chance to 3HKO after Leftovers recovery
4 SpA Clefable Moonblast vs. 0 HP / 4 SpD Mega Absol: 296-350 (109.2 - 129.1%) -- guaranteed OHKO
Aromatisse:
+2 252+ Atk Mega Absol Night Slash vs. 252 HP / 252 Def Aromatisse: 135-159 (33.2 - 39.1%) -- 13.6% chance to 3HKO after Leftovers recovery
0 SpA Aromatisse Moonblast vs. 0 HP / 4 SpD Mega Absol: 306-360 (112.9 - 132.8%) -- guaranteed OHKO
(lel get rekt)