All tiers, even Larcade. These days I don't really consider the spriggans all that different from each other, other than August and Eileen of course. For me Wahl is just as weak as Ajeel. Dimaria and God Serena are the only spriggans that really impressed me, and even then that's only because they were stomping weaklings. Doesn't mean she'd beat all spriggans though, just that I consider her more or less on they're level.
Personally I think Larcade is at the very least above all of the Spriggans bar DiMaria (and even then I'm iffy on that because he was portrayed as stronger... though I also subscribe to the logic of feats > portrayal so this is a grey area for me, Age Seal is crazy but I can't remember whether it was confirmed to be able to stop the likes of Laxus in it, I would think not though given that E.N.D just straight up said no to it).
Larcade's hax are just way too good. His Orgasm Magic is pretty much a win button, his Hunger Magic leaves opponents worn out and his Slumber Magic ends fights quickly. This dude crippled a whole battlefield including Gildarts and Laxus, and it didn't seem like it was particularly strenuous on his part. There's also the fact that he went up against his complete counter and still almost won. As much as I love that fight Sting was only ever competing because he was immune to Larcade's win button and could eat the tentacles that would get rid of said immunity. Even the ending of that fight was caused by immense luck on Sting's part. Now yes, you can argue that Sting isn't particularly powerful (I peg him as Historia S12 level), but he was amped by Rogue (I have WSDM Sting as mid-S12), immune to his orgasm hax, and had a solution to his only other "I win" button. Before Rogue gave Sting the power up he was clearly losing even despite the massive advantage he had on Larcade. I don't think there's any other Spriggan except Larcade that pulled off such a good performance against their direct counter.
As for the part about the regular S12's not being all that different... I can see what you mean because the variety of hax makes them hard to rank, but I don't think its to the level that they're on par with each other. Since you used Ajeel and Wahl as the example, I'll try and use them too.
So Ajeel's got a couple of things going for him, his sand body makes him immune to physical attacks, he's got a city-wide sand attack and he can use it to sift around on the battlefield. His sand can also drain moisture from the victim. Impressive? Maybe, but I'd argue Wahl is the harder combatant to fight. His Weakness Magic allows him to alter himself to become a counter to what he's facing, he can make weapons from thin air (Alchemy) and his damage output is dramatically more impressive. Their performances also show a difference in strength to me too, Ajeel's fight with Erza was impressive but his Sand Body mitigated a fair bit of what Erza could use (Wind/Water were the only useful Requips aside from Nakagami). He then went on to lose to
Elfman and Lisanna.
Wahl on the other hand fought a half-dying Laxus. This sounds bad but despite his condition the man still had top tier MP within the FT guild. That means a half-dying Laxus is somehow on par with the likes of Gray and Erza when looking at pure MP even in his condition. He was also showing impressive speed and strength, perhaps more so than Erza during her fight, as I can't see her replicating Laxus' bullet dodging. Regardless though, Wahl put in a good performance and showcased a number of qualities. The first is that to beat him you have to be a versatile mage, if you only have one type of Magic he's going to stomp you. Second is that he's decent in CQC and has a massive arsenal of firepower. Third is that if things are looking bad he isn't like the other Spriggans where they just default to their nuke, Wahl enters a peak version of himself where everything about him is tailor-made to kill the opponent. Admittedly though, his actual durability is somewhat hard to tell as yes Laxus did one-shot and
kill him once he got passed the immunity, but Machina are apparently just that vulnerable to electricity. What shouldn't be overlooked about that scenario is that it was a healthy Laxus that killed Wahl. Laxus at the start of the arc would have killed Ajeel with one nameless nuke if we are to believe August (and we really have no reason not to believe this). So Wahl, a being inherently weak to lightning, being killed by Laxus' named and seemingly very powerful spell is nothing to hold against him.
For these reasons I can't put Ajeel and Wahl in the same tier. Wahl is just far more dangerous to most mages as versatility appears to be quite rare in Fairy Tail.
