Ok her chains aren't as strong as Kushina's but that's because Kushina had the strongest Uzumaki chakra. The same rule applies to the Uchiha, not everyone has a Sharingan with the same level of power as Madara/Sasuke, but that does't mean they're weak.
Her chakra chains can still be used to defend against an opponent's jutsu. (chakra chains in general have offensive and defensive ability), I would say her chains were on par with ribcage Susanoo when she first unlocked them
at least. (They broke through a Mokuton jutsu) Her chakra chains aren't that strong but you forget she just recently unlocked that ability. A few years training and I'm sure her chains will match up to a Susanoo user. (normal half body Susanoo,
not PS)
Also, Karin's lack of potent chakra is compensated with a strong body. The healing ability may not regenerate but it restores chakra levels (same function as bijuu chakra but on a tiny scale)... Unlike Tsuande and Sakura, she doesn't actually need a jutsu to heal herself

Would Sakura or Tsunade survive a stab in the heart by Sasuke's chidori after already giving him considerable amounts of their chakra ? Without a byakogou, would they have survived Sasuke's Amaterasu, considering they get burnt all over her back for more than a few seconds ? She did this with
zero jutsu.
That ability to heal/restore chakra is very useful against an opponent with high chakra levels (often S-Rank shinobi), it also allows prevention from getting into serious injuries that would require regeneration. :yeah:
Her body's durability is only rivalled by Kushina and Ashura's transmigrants.
She also has good chakra control as proven with her sensing abilities, technically she also has an affinity for genjutsu since she can actually sense when someone is under one or using one.

Kushina was Kage level, Karin's an average Uzumaki that still surpasses almost every jonin
despite only having 2 forms of jutsu... (sensing and chakra chains) :yeah:
I admit her lack of ninjutsu and taijutsu almost make her useless in battles, but in terms of pure potential she could reach a level just below the Kages. Imagine if Kishi gave her ability to use elements with her large chakra reserves my gahd.
And unlike her chakra, Karin's body hasn't reached it's prime. And we know Uzumaki's potential when it comes to body strength.
I'M NOT A KARIN WANKER I'M JUST STATING MY OPINION BASED ON THE MANGA
P.S : Obito and Konan would have been the most bad ass couple. But he just had to wet himself over a dead child. :|