This team looks like its pretty good. Some first look suggestions that i would give is that you have no way to clear the field so a defoger or rapid spinner could be useful. I also noticed that you have no special attackers and that could leave you walled in some circumstances. When it comes to a special attacker I think you might want o look into mismagiusas you also have nothing that can block a rapid spin to keep your rocks on the field.
Mismagius @life orb
Abillity:Levitate
Evs 252 SpA 252 Spe 4 Def
Timid Nature
shadowball
thunderbolt
nasty plot
destiny bond/ substitute
This set works well for you as you are fairly weak to water types and will give you another sweeping option if crustle gets countered. I would replace archeops with this since you havent had luck with it but since you will be loosing a good revenge killer you will have to be careful about not sacrificing your swellow. If revenge kills become to much of a problem i would swap mismagius for scarfed typhlosion.
I would also recommend a new lead over cradily. Considering all you are really doing with this thing is setting rocks up and possibly poisoning a pokemon I think you could do better. I would recommend using steelix.
Steelix @leftovers
abillity:sturdy
Evs 252 hp 252 SpD 4 Atk
Careful Nature
Stealth rocks
earthquake
Iron head
Roar
Steelix will always get rocks up with sturdy and woth roar is a fantastic way to stop any boosted sweeper if it his high enough hp. It also can do fairly good damage with earthquake and iron head and walls many common threats to NU.
Lastly you might want to swap boomburst on swellow with quick attack for some strong priority and of your not getting enough power from it you could sacrifice more of its health with a toxic orb but loosing the attack halving effect.