Mega Blaziken with Moxie isn't even better than the Speed Boost version since getting all the Speed boosts is what makes Mega Blaziken insane.
+2 252 Atk Life Orb Tera Ice Baxcalibur Icicle Crash vs. 248 HP / 252+ Def Corviknight: 364-429 (91.2 - 107.5%) -- 43.8% chance to OHKO
+2 252 Atk Sharpness Gallade-Mega Sacred Sword vs. 248 HP / 252+ Def Corviknight: 367-433 (91.9 - 108.5%) -- 50% chance to OHKO
Just look at this calc, Sharpness Mega Gallade's Sacred Sword is stronger than Life Orb Tera Ice Baxcalibur's Icicle Crash, and Bax was a mon that basically had no switch-ins in OU. Yes, I realize that Fighting/Psychic/Dark is not as offensively potent as Ice/Dragon/Ground, but I think you undersell how strong Mega Gallade with Sharpness would be. The reason Samurott-Hisui is balanced is 'cause of its relatively mediocre Base Attack, the low Base Power of its moves, and its middling speed, but with Mega Gallade, it'll get STAB Sacred Sword as well as having good speed for a wallbreaker, which is more than enough to be a top threat in OU.
And pika pal, you should calc with Close Combat for Mega Gallade since you didn't give it Sharpness. It's not a fair comparison to not use Mega Gallade's best STAB attack for a comparison like that.
I calc'd using Sacred Sword because the main point of the demonstration was that Sharpness is a bigger boost than the raw ATK buff, while also advantaging Gallade over CC by not reducing its already Meager defenses (and thus making it even more vulnerable to chipped Revenge Kills).
252 Atk Gallade-Mega Close Combat vs. 0 HP / 4 Def Manaphy: 234-276 (68.6 - 80.9%) -- guaranteed 2HKO after Leftovers recovery
252 Atk Gallade-Mega Zen Headbutt vs. 0 HP / 4 Def Manaphy: 156-184 (45.7 - 53.9%) -- 3.1% chance to 2HKO after Leftovers recovery
252 Atk Sharpness Gallade Sacred Sword vs. 0 HP / 4 Def Manaphy: 213-252 (62.4 - 73.9%) -- guaranteed 2HKO after Leftovers recovery
252 Atk Sharpness Gallade Psycho Cut vs. 0 HP / 4 Def Manaphy: 166-196 (48.6 - 57.4%) -- 49.2% chance to 2HKO after Leftovers recovery
As also demonstrated here, Close Combat is the only case where Mega Gallade out damages Sharpness since it's the only move with that high a natural BP due to the drawback nature.
The Baxcalibur comparison is also missing the context that Baxcalibur was broken by a variety of sets that shored up its survivability (Veil + Snow = Easy Boosts). Mega Gallade does not get free Swords Dance to the extent Bax got them or DD, nor does it have traits like Burn immunity or set variety to force prediction like the Ice Body/Sub sets.
252 Atk Great Tusk Close Combat vs. 0 HP / 0 Def Baxcalibur in Snow: 284-336 (76.5 - 90.5%) -- guaranteed 2HKO
+1 252 Atk Baxcalibur Glaive Rush vs. 0 HP / 4 Def Mew: 316-373 (92.6 - 109.3%) -- 56.3% chance to OHKO
+1 252 Atk Baxcalibur Icicle Crash vs. 0 HP / 4 Def Mew: 225-265 (65.9 - 77.7%) -- guaranteed 2HKO
+2 252 Atk Baxcalibur Glaive Rush vs. 0 HP / 4 Def Mew: 423-498 (124 - 146%) -- guaranteed OHKO (Keep in mind all of these calcs are without its item)
Baxcalibur is slightly weaker for significantly less commitment, and this is mostly looking at power output. The sheer neutrality of Glaive Rush + Ice and Ground coverage means this power goes a lot further into the majority of opposing mons.