Had to test Alakazam a fair bit to gain a better insight into how it plays in the tier. Counter-sash Zam is very straight forward & 1-dimensional - and could be considered effective, having faced and used it myself I know that it is certainly a nuisance and great at what it does; but I don't believe it is ban worthy on its own. This version of Alakazam, whilst great versus opposing HO builds, is very manageable versus BO & Balance builds. Let's take this set and look at it on its own.
In the case of bulky offence and balance, sash Alakazam users face the problem of being 1-dimensional - this particular set is not difficult to switch into and can be used as set up for Pokemon such as Hippowdon. On the subject of Hippowdon; Psychic fails to 2hko, Hippowdon attains SR and, it can Whirlwind out Alakazam if the user is aware of Counter. As you can see, this is an all too familiar scenario for users of Sash Zam considering they forego coverage and Thunder Wave, Pokemon such as; Latias, Slowbro, Clefable, Scizor (free defog), Mew, Hippowdon, Klefki, Primarina, Swampert, etc. all become reliable stops to it - dependant on the coverage in most cases (which is not difficult to scout).
According to the
Smogon Stats for February, Sash Zam is seen approx. 59% of the time. Though I do not recognise the accuracy of these statistics, given the youth of the current metagame, I would like to point out how common this version of Alakazam appears to be. [edit: I would like to point out that these stats do not reflect the usage of Counter on Alakazam, point being, it wasn't a very well known set at the time. I was just using this to show how common Focus Sash is on Alakazam].
I will not discredit Focus Sash Alakazam versus offence builds at all, it's very effective. However, I would now like to discuss the other side of the coin, LO CM Alakazam - approx. 38% usage on ladder. This version of Alakazam in conjunction with the previously explored set is what makes it such a terror to face. Although not as common, LO CM Alakazam manages to threaten all versions of play style very easily. With Life Orb equipped, and coverage in Psychic, Focus Blast & Shadow Ball, Alakazam has no current switch ins once it gets to +1. Furthermore, it doesn't require +1 to do damage to opposing teams.
Seeing as 2/5 of Alakazam are LO, I would consider this set as not insignificant, that is, most adept players are wary of this sets existence; and the level of uncertainty alongside that creates a problem. Given the fact that Alakazam has the tools to beat all play styles, as well as a completely different list of checks and counters based primarily on which set it chooses to run - I have made an assessment.
I have come to the conclusion that Alakazam is indeed too strong for the tier, Sash Counter Zam is a legitimate threat to the tier and although easy to handle for bulkier builds; they are promptly shredded by the lesser used LO CM Zam set, which threatens all play styles. Both sets in conjunction with one another create a level of uncertainty for the player, especially considering their differing checks & counters. Alakazam has, once again, been pushed over the edge.
Edit: I've only explored two of Alakazam's most relevant sets and their influence on the metagame. The fact of the matter is that Alakazam has other, lesser used options, that also allow it to disrupt the meta, those being: Encore, Thunder Wave & Substitute.