Don't use This:
Bastiodon @ Leftovers
Ability: Sturdy
EVs: 252 HP / 4 Def / 252 SpD
Careful Nature
- Stealth Rock
- Toxic
- Roar
- Magic Coat / Metal Burst
I've seen quite a few Bastiodon on the low ladder and i honestly don't know why. At first glance it's Defense-Stats look very nice for a Stealth Rocker and Mixed Wall, but then you realize how bad it's Typing is defensively with that nasty 4x Fighting- and Ground-Weakness, which hinders it's ability to check Normal- and Flying-Types and either Physical and Special Attackers in general. It's also extremely passive due to very low attacking stats and no attacking move, so many Pokemon (especially the very common and threatening Machoke) can come in almost for free and start to threatening it. Also without the recommended Magic Coat, every random Pokemon with Taunt completely stops it in it's tracks, which really sucks. Many of these flaws also apply to Probopass, who struggles quite a bit in the current Meta, but at least it has a slow Volt Switch to gain Momentum, Magnet Pull to Trap and Kill Pawniard with a bit Prior-Damage and weakening Metang for other Teammates (although Sturdy seems to be more useful in the current meta). There are also other Bulky Stealth Rocker who all get the job way better done and have some good niches, which many teams really appreciate while Bastiodon is completely outclassed and deserving of it's E-Rank Status in the VR.
Instead, use one of these:
Golem is one of the best Pokemon in the tier and fills - depending on the playstyle of the team - different roles very effectively. The sturdy suicide lead with WP / Custap Berry is one of the best suicide leads in the tier with monferno and gets almost assured sr on the field early game. It can also become very threatening with a weakness policy boost, revenge kill weakened threats with sucker punch or blow up with custap explosion and can still be used as a choiced flying-, normal- and electric-check, if really needed, while the spd set with toxic + protect is a really nice normal-, flying- and electric-check, can get stealth rocks up throughout the game + scouting moves from choiced mons and can even stall a bit with toxic + protect.
Gabite is, thanks to Eviolite - really sturdy on the physical side and is unlike most other Stealth Rocker not very weak against fighting-, physical water- and Grass-types like any Monferno, CB floatzel, Leafeon, Sawsbuck and physical based Simisage-Sets. It can also soft check choiced electric-types, Relicanth and Rampardos, countering Arbok and it also checks Fire-Types like Rapidash, Ninetales and Simisear. It also beats most common Stealth Rockers in the tier like Golem, Camerupt, Stunfisk, Metang and even Relicanth 1on1, which is really cool. It really likes Wish-Support though, to check all the aforementioned threats reliably and to get stealth rocks on the field throughout the game.
Camerupt is one of the best Electric-Type Checks in the tier, can soft check ice types like Rotom-F, Regice, Articuno etc., special Fire-Types like Ninetales and Simisear, Klang etc. It can also forme many good Balance-Cores like Camerupt + Roselia / Tangela / Gourgeist-super + Politoed / Lapras or Camerupt + Altaria + bulky water / bulky grass type, beating a few Stealth Rockers like Probopass, Metang and Stunfisk 1on1 and can also get stealth rocks up multiple times, it hates like bulky water defogger like Lumineon and Prinplup though (although all stealth rockers in the tier bar maybe stunfisk don't really like them either, most of them can cripple them with toxic though) and appreciates Wish Support to not get worn down too fast.
Stunfisk is one of the best blanket Electric-Type Checks in the tier and only really fears Blizzard from Rotom-F and LO / Choice Specs Surf from Raichu, while at the same time checking Arbok, Monferno, Pawniard, Mightyena, Dodrio, Stoutland (although there are better Stoutland-Checks out there), Rapidash and Mukrow with max. Def or countering most Electrics and checking Chatot, Ninetales, Simisear and Mr. Mime with max. SpD.
It also fares pretty good vs most defogger and rapid spinner in the Tier like Vullaby, Prinplup, Lumineon and Vibrava after toxicing it on the switch, it loses against Cryogonal, Armaldo and after bit Prio-Damage to Swanna 1on1 though, so Teammates who can get rid of these Pokemon are very appreciated. Like basically all other Bulky Stealth Rocker it also appreciates Wish Support from Audino (its not really nessecary though).
Metang is one of the best Psychic and Ice-Type Checks in the tier, namely Mr. Mime, Grumpig, Beheeyem and Kadabra + Regice, Articuno, Cryogonal, Beartic and Glaceon. It also checks Normal- and Flying-Types like Dodrio, Chatot and Jumpluff (only after it put something to sleep with sleep powder though) + Stoutland, Sawsbuck and Purugly and can get up Stealth Rock pretty easily on the field. Thanks to access to Pursuit, it can trap aforementioned Psychic-Types and can also get chip damage on locked Choice-Attackers. It tends even more than most other Stealth Rocker to get worn down fast though and loses vs most defogger and rapid spinner 1on1, so it depends heavily on other Pokemon to get rid of the Pokemon, who hinder it at getting one of it's main jobs done and very appreciates Wish Support.
Relicanth is one of the best Normal- and Flying-Checks in the tier, like Dodrio, Murkrow, Drifblim (only the Acrobatics-Set though) Stoutland (it hates CB / LO Superpower though), Chatot and Purugly. It also checks threatening Dark-Types like Pawniard and Mightyena + physiscal Fire-Types like Rapidash (it hates Will-O-Wisp Burns though), physical Altaria-Sets, Ninjask etc. It's main niche lies in Rock Head Head Smash though, which gives it a very good offensive presence and lets most defogger and rapid spinner think twice before coming in and trying to get rid of Stealth Rock, so it very reliably gets Stealth Rock up and often they end up staying on the field. It also can run an even more threatening Choice Band-Set, which is one of the most fearsome Wallbreakers in the tier and has got very few switch-ins and a Rock Polish-Set for Lategame-Cleaning.
All of these mentioned Pokemon are really good in this tier and do their jobs way better than poor Bastiodon could ever dream of.
Edit: Just saw, that Raiza posted Bastiodon on page 1 one year ago, i will put up another bad pokemon / set later today or tomorrow though.