The Akatsuki is generally composed by the strongest S-rank missing nin, so of course Hidan is very strong. Tobi and Pain invested a lot of time in choosing powerful members, not weaklings. This premise being made, it's pratically universally recognized that Akatsuki's fighting prowess has a hierarchy.
Tobi, Pain and Itachi are undoubtedly too strong for basically everyone. If you sum all three's battles together you get only one loss (Naruto vs Pain), everyone else has bitten the dust against those, except Minato but those where Tobi's first years. Count that Itachi is stated at 35.5 like Jiraiya, Pain has defeated Jiraiya albeit with the surprise effect (so it must be at 35.5 or higher) and Tobi has to be comparable to Pain.
Sasori and (at his own time) Orochimaru are repeatedly stated to be comparable in power (34.5 and 35), with Orochimaru being a little superior. They are stated to be above most Akatsuki members but the manga implies often than the top three whould just walk over these two without much problems.
Deidara, Kakuzu and Kisame are all very powerful (32.5) and - more importantly - all of them had "surprise moves" that can put them above an unaware opponent. Notice for instance how Kakuzu was stomping Kakashi, Ino and Choji even after his very effective team mate had departed. Kakashi is explicitly stated to be stronger than Kakuzu (34.5) but was still going to fall because he didn't understood Earth-Grudge-Fear too well. But despite being that powerful they just don't compare to the top tiers nor to the high tiers. Which is something they even state by themselves.
It is widely recognized that Konan, Hidan and Zetsu are below those. They're of course much stronger than any everyday shinobi - compare Hidan, 31.5, to shinobi like most of the Konoha 11 who are recognized universally as pretty good in their fields and whose power is ranked around 20. But they aren't on par with what the rest of the Akatsuki can dish out (I am a bit doubtful about Konan though, because we know Hidan stats and Zetsu is explicitly stated to be the weakest, but we don't have many objective measurings on her).
These three "low tiers" also have special reasons to be active Akatsuki members. Konan is a master at camouflaging and protecting Pain's body. Zetsu is a special ops agent like Tobi could only dream. And Hidan is an extraordinary effective partner for Kakuzu and is probably the best partner EVER for just anyone who has a big-scale ninjutsu undiscriminated style of attack, because he's probably the only one who can keep fighting with little problems while under massive friendly fire (except reincarnated shinobis).
Speaking of Hidan specifically, his value outside of partnership with Kakuzu is limited. He is a strong taijutsu user with a very uncommon fighting style, and he is very hard to cripple him with normal wounds, one should just sever his limbs to incapacitate him (again, a drawback nullified by his partnership with Kakuzu). That is effective, but not unbeatable, allows many countermeasures (immobilize with traps or ninjutsu, genjutsu, fuinjutsu, or, well, just sever the limbs). He relies a lot on abusing the Death Possession Blood curse which, as Shikamaru says, it's useless once you saw it once because it requires too many steps and is easy to interfere with, unless one as some sort of backup cover (again: Kakuzu). If you sum this up, Hidan is a very resilient and damaging tank that can sometimes pull a killing trick. There are at least seven Akatsuki members who are clearly above this.
