Your team has three major weaknesses, although one of those is in the category of one of the others. First off is the fact that the majority of your team is composed of physical attackers, allowing a physical wall/tank such as Tangela, Gigalith, Alomomola to easily wall your team and do as they wish. The second weakness is strong physical attackers, such as Sawk, Gurdurr, and Swellow. And the third weakness is a strong physical attacker, but one worthy of such note because it manages to easily destroy your team. That weakness is Golurk, who Raichu does the most damage to with Grass Knot, which happens to be only 83% - 98.2% to a standard 248 HP Golurk, meaning that while you are able to revenge kill Golurk after Grass Knot, you will have lost Raichu in the process.
Now then, one of the best measures for all of these problems is going to be adding a Tangela to your team. It can take pretty much every physical attacker in the game. Those it can't take it will easily neutralize with Sleep Powder. Tangela also manages to outspeed Golurk. As such, adding a Tangela to your team should be your first priority.
Next is some more bulk, yet also some Special offense. Duosion is an excellent Pokemon who can help deal with the Fighting type menace while also taking hits from other foes quite well. We'll replace Audino with that.
Tauros and Swellow pretty much do the same job. I found Tauros to be more effective for your team, and it is a lot harder to counter due to its movepool, so we'll keep Tauros and kick out Swellow. In return we'll add a Machoke, who is another bulky Pokemon but is better able to deal with opponent's thanks to Dynamicpunch, as Confusion can screw over any potential counters.
Now with the Pokemon swaps out of the way we can deal with the rest of your team.
We have Articuno being used as an attacker. The set that Dr. Flame posted should be used as it is superior to an attacking Articuno. With Machoke support you are also able to take down Mawile, Bastiodon, and Probopass, who threaten the set by walling it completely.
I would give Regirock Thunder Wave instead of Toxic. Regirock will usually attract set up Pokemon (hopefully Gurdurr and Throh aren't attracted, as they are as hard of counters as you can get to Regirock) such as Gorebyss, and Thunder Wave is better able to take care of them. And instead of Protect, I would run with Earthquake, as Regirock has decent offenses and Earthquake gives you the classing Edge-Quake combo of type coverage.
Tauros doesn't have that great of a set. It likes having Return/Frustration so it doesn't get taken out by recoil combined with priority being launched at it. And Iron Head and Outrage do not provide good coverage. Instead give it Stone Edge and Zen Headbutt. Then as Dr. Flame suggested, a Choice Band will do you good. Then give it a Jolly Nature so it can outspeed stuff.
As for Raichu, I find having at least one Scarfer on a team is a neccessity. So we'll give it a Choice Scarf and swap out Nasty Plot and Thunder Wave for HP Ice and Focus Blast.
Regirock @ Leftovers
Trait: Clear Body
EVs: 248 HP / 8 Atk / 252 SDef
Careful Nature (+SDef, -SAtk)
- Thunder Wave
- Stone Edge
- Earthquake
- Stealth Rock
Articuno @ Leftovers
Trait: Pressure
EVs: 248 HP / 8 SDef / 252 Spd
Timid Nature (+Spd, -Atk)
- Ice Beam
- Roost
- Substitute
- Toxic
Machoke (M) @ Eviolite
Trait: No Guard
EVs: 248 HP / 252 Atk / 8 Def
Adamant Nature (+Atk, -SAtk)
- Bulk Up
- DynamicPunch
- Payback
- Bullet Punch
Tauros (M) @ Choice Band
Trait: Intimidate
EVs: 252 Atk / 4 Def / 252 Spd
Jolly Nature (+Spd, -SAtk)
- Frustration
- Earthquake
- Zen Headbutt
- Stone Edge
Tangela (F) @ Eviolite
Trait: Regenerator
EVs: 248 HP / 252 Def / 8 SAtk
Bold Nature (+Def, -Atk)
- Giga Drain
- Hidden Power [Ice]
- Sleep Powder
- Leech Seed
Raichu (M) @ Choice Scarf
Trait: Lightningrod
EVs: 252 SAtk / 4 SDef / 252 Spd
Modest Nature (+SAtk, -Atk)
- Thunderbolt
- Grass Knot
- Hidden Power [Ice]
- Focus Blast
