With Sound moves now hitting through Sub, and the popularity of Hyper voice, Boomburst, and other sound based moves, this set could have some trouble against some pokemon
As an aside: You should really add more to your post when saying things like this. Listing Pokemon, running damage calculations, potential threats, what have you, all add more to the conversation than one-liners do.
That said, all sounds moves are Normal Type, or, after Pixilate, Fairy-Type, meaning Mawile resists all of them, and 50/95 ain't too shabby when it comes to taking resisted assaults. In addition to that, the only common users of sound-based moves are Sylveon, Gardevoir, Exploud and Noivern, 3 of which Mega Mawile beats without any concerns at all, and one of which (Noivern) Mega Mawile struggles to beat, but not because of Boomburst, but because of Infiltrator, which lets him bypass the Substitute and nail him with a Flamethrower.
Damage Calculations
vs. 164 HP/0 SDEF (Adamant) Mega Mawile
0 SATK (Calm/Bold) Sylveon Hyper Voice (119 Base Power): (25.53 - 30.49%) -- guaranteed 4HKO.
252 SATK (Modest) Exploud w/Life Orb Boomburst (140 Base Power): (47.16 - 55.67%) -- 77.34% chance to 2HKO
252 SATK (Timid) Mega Gardevoir Hyper Voice (119 Base Power): (42.9 - 50.7%) -- 2.34% chance to 2HKO.
252 SATK (Timid) Noivern w/Life Orb Boomburst (140 Base Power): (59.92 - 70.92%) -- guaranteed 2HKO.
252 SATK (Timid) Noivern w/Life Orb Flamethrower (90 Base Power): (78.36 - 92.19%) -- guaranteed 2HKO.
252 SATK (Timid) Noivern Flamethrower (90 Base Power): (60.28 - 70.92%) -- guaranteed 2HKO.
Mega Mawile vs.
252 ATK (Adamant) Mega Mawile Play Rough vs. 252 HP/0 DEF (Calm) Sylveon: (100 - 118.02%) -- guaranteed OHKO.
252 ATK (Adamant) Mega Mawile Play Rough vs. 0 HP/0 DEF (Naive) Exploud: (116.04 - 136.67%) -- guaranteed OHKO.
252 ATK (Adamant) Mega Mawile Sucker Punch vs. 0 HP/0 DEF (Naive) Exploud: (68.76 - 81.08%) -- guaranteed 2HKO after Stealth Rock
252 ATK (Adamant) Mega Mawile Sucker Punch vs. 0 HP/0 DEF (Timid) Mega Gardevoir: (84.47 - 99.63%) -- 75% chance to OHKO after Stealth Rock.
252 ATK (Adamant) Mega Mawile Play Rough vs. 0 HP/0 DEF (Timid) Mega Gardevoir: (142.23 - 167.87%) -- guaranteed OHKO.
252 ATK (Adamant) Mega Mawile Play Rough vs. 0 HP/0 DEF (Timid) Noivern: (214.79 - 253.37%) -- guaranteed OHKO.
252 ATK (Adamant) Mega Mawile Sucker Punch vs. 0 HP/0 DEF (Timid) Noivern: (63.66 - 75.24%) -- 6.25% chance to OHKO after Stealth Rock.
0 SATK (Calm/Bold) Sylveon Hyper Voice (119 Base Power): (25.53 - 30.49%) -- guaranteed 4HKO.
252 SATK (Modest) Exploud w/Life Orb Boomburst (140 Base Power): (47.16 - 55.67%) -- 77.34% chance to 2HKO
252 SATK (Timid) Mega Gardevoir Hyper Voice (119 Base Power): (42.9 - 50.7%) -- 2.34% chance to 2HKO.
252 SATK (Timid) Noivern w/Life Orb Boomburst (140 Base Power): (59.92 - 70.92%) -- guaranteed 2HKO.
252 SATK (Timid) Noivern w/Life Orb Flamethrower (90 Base Power): (78.36 - 92.19%) -- guaranteed 2HKO.
252 SATK (Timid) Noivern Flamethrower (90 Base Power): (60.28 - 70.92%) -- guaranteed 2HKO.
Mega Mawile vs.
252 ATK (Adamant) Mega Mawile Play Rough vs. 252 HP/0 DEF (Calm) Sylveon: (100 - 118.02%) -- guaranteed OHKO.
252 ATK (Adamant) Mega Mawile Play Rough vs. 0 HP/0 DEF (Naive) Exploud: (116.04 - 136.67%) -- guaranteed OHKO.
252 ATK (Adamant) Mega Mawile Sucker Punch vs. 0 HP/0 DEF (Naive) Exploud: (68.76 - 81.08%) -- guaranteed 2HKO after Stealth Rock
252 ATK (Adamant) Mega Mawile Sucker Punch vs. 0 HP/0 DEF (Timid) Mega Gardevoir: (84.47 - 99.63%) -- 75% chance to OHKO after Stealth Rock.
252 ATK (Adamant) Mega Mawile Play Rough vs. 0 HP/0 DEF (Timid) Mega Gardevoir: (142.23 - 167.87%) -- guaranteed OHKO.
252 ATK (Adamant) Mega Mawile Play Rough vs. 0 HP/0 DEF (Timid) Noivern: (214.79 - 253.37%) -- guaranteed OHKO.
252 ATK (Adamant) Mega Mawile Sucker Punch vs. 0 HP/0 DEF (Timid) Noivern: (63.66 - 75.24%) -- 6.25% chance to OHKO after Stealth Rock.
Every one of these Pokemon threatens to deal massive damage to Mawile - however, Noivern is the only one who can outright kill him while he's behind a Substitute, but not without taking massive damage and potentially killing himself from the combination of Sucker Punch, Stealth Rock, and Life Orb recoil.