I believe klang, relicanth, and Avalug should rise, while barbarcle and carracosta should be lowered.
Klang is so strong against an ice spam tier. All of the ice pokemon seemed to drop to pu, and klang is probably the strongest offensive steel type above metang. Klang cannot have it's stats lowered by intimidate or sticky web because of the marvelous clear body. Once it sets up ~2 shift gears (which isn't too hard with it's steel typing/eviolite bulk) it can sweep teams without a resistant physical tank. Being immune to toxic is also invaluable, because stall works so incredibly well in this tier mostly thanks to licki. The only problem I have with klang is that it has one set, and that is - shift gear/return/gear grind/wild charge.
All I have to say about relicanth is that it resists fire and ice, which are 2 very important types in the tier, but is weak to grass, and there are grasses all over this tier as well. He is also bulkier than carracosta. It should be higher though, because practically nothing that does not resist rock can switch in on it.
252+ Atk Choice Band Relicanth Head Smash vs. 252 HP / 252+ Def Lickilicky: 234-276 (55.1 - 65%) -- guaranteed 2HKO after Leftovers recovery
252+ Atk Choice Band Relicanth Head Smash vs. 252 HP / 252+ Def Eviolite Piloswine: 174-205 (43 - 50.7%) -- 96.9% chance to 2HKO after Stealth Rock
252+ Atk Choice Band Relicanth Head Smash vs. 252 HP / 252+ Def Eviolite Tangela: 136-162 (40.7 - 48.5%) -- 67.2% chance to 2HKO after Stealth Rock
These calcs just show that these prominent physical tanks cannot switch into head smash and stay in safely. Though, in tangela's case, you need speed evs, because tangelas a quick lil devil at 60 base speed
Barbaracle and Carracosta should be lowered because their shell smash sets are old and obvious and can be checked by the bulky grass types, taunt, encore, WoW, etc etc. Barbarcle has no other set than shell smash. Carracosta has other sets which makes him more unpredictable and better, but they are both forced to switch at any grass type, and this tier has loads of grass types.
I just mentioned avalugg because he is probably the best spinner, and even though he is ice type, his defense makes him take super effective hits well unless boosted/banded.
VIBRAVA
I'm really surprised vibrava is not on the list. I actually think vibrava is one of the best defoggers in the tier, and based on your team, he could be the best defogger for you. Dragon typing gives good resistances to fire, grass, water, and it's immunity to electric is great. Vibraba is the BEST defogger for longevity because it has roost, can switch into all spikes, and web and take no effect because levitate, and it resists SR like a champ because it isn't flying and its ground typing resists rock. Many rock setters are also rock typed, and hate to get hit by stab EQ.I run Roost,defog,EQ,U-turn/toxic. 252hp/252def, eviolite. I would put him C+ tier in the LEAST.