Here is a Whirlipede set I was using before Roselia dropped. It is slightly outclassed, but it has a few things that Roselia does not, namely better defences and Struggle Bug.
Whirlipede @ Eviolite
Trait: Quick Feet
EVs: 252 HP / 252 SpDef / 4 Def
Calm Nature
- Spikes
- Toxic Spikes
- Rest
- Struggle Bug
Welcome to the most single minded Pokemon you have seen. Whirlipede usually has one and only one goal, setting up Spikes. Unfortunately, Whirlipede is complete set up fodder, even if I run max attack, as its strongest attack is Steamroller, which is where Struggle Bug comes in. It allows various special based 2HKOs (like Ludicolo and Samurrot) to turn into 3-4HKOs, which allows Whirlipede to set up more spikes, force switches and make my switching easier. Alomolomolomolomolomola might not like Ludicolo much, but at -2, Alo can start passing Wishes and heal the team. Rest is for healing and to frustrate special walls even more, and because Whirlipede's movepool is terrible.
Against most physical attackers, Whirlipede relies on its naturally high defence. It cannot come in on powerful neutral STABs, like from Zangoose, Ursaring and Sawsbuck, but it can come in on Ice Punches or Close Combats from Sawk. Gurrdurr cannot do much to Whirlipede, but neither can Whirlipede, so Gurrdurr can joyfully set up infront of Whirlipede and eventually beat it after a few Bulk Ups. The same can be said of Braviary, possibly to devastating effects, so viable Physical Walls (hopefully with Roar) are needed to take those hits. Bastiodon can utilize Whirlipede's 4x fighting resist to take the Flying and Psychic attacks aimed at it. Healing is also pretty useful, as Whirlipede is weak to SR and Spikes, which will force it to rest more often. As such, a Cleric can also be used to wake Whirlipede up after it rests.
Also, despite its SpDef investment, powerful attackers like Musharna and Gardevoir can KO Whirlipede, although Whirlipede can leave two parting Struggle Bugs with Musharna. Regice can also fire off semi-powerful Thunderbolts thanks to its SpAtk preserving Clear Body. Whorlipede is alsovulnerable to Trick varients of Rotom, but it can usually take on non-Trick Rotom-Frost thanks to being nuetral to Blizzard.
Sadly, as I said, Whirlipede is almost completely outclassed by Roselia, who can set up both Spikes, but can use Leech Seed, SleepPowder, and its competent SpAtk to actually do some damage. But, I find Whirlipede has some great resistances (4x Fighting and no Ice weakness) and a great Defence, so it might find a very small niche in a team that likes Struggle Bug. It just requires too much team support to function.