Mixed typing movesets even less desirable now?
It was quite rarely the case that a mixed moveset was more useful than a mono type moveset on offense, but with weather boosts going on this seems like even more of a concern, with some pokemon being in the unfortunate sitation of having one of their optimal moves boosted while leaving the other unboosted. There seems to be even less of a case for mixed movesets now. Some examples:
Exeggutor Confusion/Solar Beam
Mewtwo Confusion/Shadow Ball or Focus Blast
Rhydon Mud Slap/Stone Edge (the best for pure DPS, although not the best use of Rhydon)
Charizard Air Slash/Overheat (Charizard's only real niche is in flying DPS, even mentioned by gamepress, but swapping to the fire type moveset just makes it a worse firebird)
Gardevoir is a weird ball because it doesn't really have another option- but nonetheless, weather boosts does not affect both of confusion and DG at the same time.
Some previous niche users for certain matchups include Bite/Hydro Gyarados and Snarl/WC Arcanine, though they are less of a concern than above.
EDIT: Also Suicune Hidden Power Rock/Fighting!!!
Some of the luckier ones include dragonite in which DT/Hurricane as both get boosted. Lugia with ES/Sky Attack also hits the jackpot. Not every pokemon is so lucky though.
Answers
Still on holidays vacation and have some sort of sinus infection...so I bothered to look at it a few minutes.
Semi-relevant recent raid: Suicune Ex/Hydropump vs perfect level 35 Sceptile in clear weather: Bullet Seed/Leaf Blade wins in 796 sec. Fury Cutter/Leaf Blade wins in 802 sec.
Neutral/Extreme weather: Fury Cutter/Leaf Blade wins 936 sec. Bullet Seed/Leaf Blade wins 945 sec.
Bullet Seed and Astonish are just really weak moves. Charge Beam is marginally better, but not by much. They need to be buffed, either by reduced time or increased damage.
From what I remember when I last checked PokeBattler, Bullet Seed is only better than Fury Cutter when hitting double weakness, and even then only slightly better. Clear skies doesn't improve it that much... sometimes clear skies even raises Fury Cutter/Leaf Blade more than Bullet Seed/Leaf Blade.
Sceptile is a bit of a glass cannon and Bullet Seed is never boosted anywhere near enough to be worth the trade-off in dodging.
It's not like they are more bad, per se, since weather doesn't negatively affect anything, but for sure they don't get the best bonus in weather favorable to one move and not the other. Still, it comes back to the point I've made about the weather mechanic ever since it came out, it doesn't make any choice worse, just makes optimal choices even better.
