In what way is Cloyster not stupidly broken in this? After a Shell Smash, each hit of Icicle Spear has a ridiculous 145 BP, letting it potentially OHKO even Max HP/Max Defense Heatran after Stealth Rocks damage. Scarf users that might outrun? Turned into putty by a 160 BP Ice Shard. Excadrill in sand? OHKO'd by Ice Shard. Scarf Kartana? OHKO'd by Ice Shard. Max attack technician CHOICE BAND Scizor's Bullet Punch doesn't OHKO Cloyster either, even after the defense drop from Shell Smash, while Icicle Spear OHKO's any possible Scizor variant, even Max Defense Mega Scizor.
Even Mega Slowbro, one of the bulkiest resists to Icicle Spear in the game, is OHKO'd.
Also, why is Kang unbanned and why is Technician banned? Tech would stop working after the moves have accumulated boosts so it's not exactly much better than in standard, whereas Kangaskhan is more broken than ever, since power-up-punch's boosts are even more effective than in the past.
So anyway, while multi-hit moves may prove to be a problem, Cloyster specifically needs to be quickbanned due to the combination of Skill Link, Multi-hit moves and most importantly, a +6 boosting move. Mega-kang probably shouldn't be sticking around either, but it's not quite as pressing.
Anyway, some other scary stuff:
Up to this point Mimikyu required a combination of Shadow Sneak and Shadow Claw to get the job done, as the former simply didn't carry enough power behind it to break through many common threats. Now however, Mimikyu can run Z-Splash to bring Shadow Sneak's power up to a devastating 100BP at +3 Attack, while running having an extra slot in it's moveset for coverage. Near guaranteed set-up opportunities assure that Mimikyu is worth looking out for.
Z-Conversion is straight up absurd, but wait, only 60 BP moves are affected by this meta, so how threatening can it be? Pretty threatening, as Porygon-Z can convert into Electric and proceed to ruin your day with a 150 BP Charge Beam now backed with Adaptability STAB, bringing it's BP to 300 and due to the nature of charge beam, 340 the next turn, 380 the next, so on and so on until your team is dust. Running either scarf or ground types will be essential to taking GonZ out, as it's capable of 2HKOing even Eviolite Chansey after Z-Conversion.