I can understand why you would question Mesprit's place in the tier
sanjay., as it does have several usable sets, decent natural bulk, offers a soft ground resist with levitate, can adapt to certain teams with slight tweaks in coverage (i.e. I used Knock Off on my rocks set to help my match-up vs stall, specifically Bronzor) and does role compression fantastically. Like it has been said however, that doesn't make it broken per-say, but just an extremely effective mon in the current metagame.
I disagree with this. Your team will not automatically get better by adding a mesprit to it every time you decide to do so. If Mesprit was mandatory on teams, like Mega Steelix and Sneasel were in their respective metas, I'd be inclined to agree that it should be suspected. However, this is not the case as each Mesprit set is not strong enough in its own right to try and warp teams to always have a focus on it. Is it a common pick because of its diversity in sets and ability to cover a sizeable swathe of niches in one slot? Hell yeah it is. However, there is a fine line between "role compression in one slot that allows it to be a common choice" and "every team has this mon and makes matchups against it unfair because it's too good to pass up."
I however disagree with what
Disjunction said about it not being making most teams 'automatically better'. While it isn't a mandatory mon in comparison to something like Primal-Groudon, it is able to easy fill holes in many teams and is usable on basically every single archetype bar stall, due to its versatility. It is
the most splashable mon in tier bar none and is extremely useful for patching up spots on a lot of teams, with most benefiting from it being there. While its defensive set struggles to deal with some common threats in the metagame, it provides momentum
and defensive synergy all at once, which is pretty much unique for a rocker in this tier; whilst also not losing to most of the dark types in the tier thanks to Colbur Berry plus U-turn.
This seems to be your main argument as to why Mesprit is broken, but there are many other instances of Pokemon in NU having role compression. Rhydon is a bulky Normal-, Flying-, Bug-, and Fire-type check that can provide an Electric immunity to the team. It also has awesome offensive presence with Swords Dance, EdgeQuake coverage, Megahorn for Torterra/Claydol who are the only two relevant mons that resist EdgeQuake coverage, and supplies invaluable Stealth Rock support.
Rhydon's assortment of roles has a similar effect on teambuilding. Dominant Pokemon in the metagame will do that and yet I haven't seen any particular reason as to why Mesprit is breaking this mold at all.
While I'm not giving this as a reason to Mesprit being broken, because it's not, I don't think this is a good comparison. You
know what Rhydon does and it almost never changes its set to utilise coverage options because it would be an unviable option to do so; unlike Mesprit which can often do it freely without compromising its current set. While Double Dance Rhydon is arguably one of the best sweepers in the meta, offering both offensive and defensive role compression, the fact that you know what set it is makes it far more manageable compared to Mesprit, as whilst on some teams its easy to see what set it is (rocker on a team without a rocker), knowing what offensive set its running could be game changing due to the different offensive sets breaking and beating different things. This tier also somewhat struggles with psychic types, due to the coverage they bring and the fact that most 'resists', aren't actually resists (see dark types and things such as Steelix) meaning it can be progressively harder to check, with sets starting to adapt vs it. Something which Rhydon hasn't really made it do.
The Stealth Rock set also has to be afraid of Toxic, Klinklang, Rotom, Mega Audino, Ferroseed, SD Samurott, and about ten or fifteen other mons. It's passive and doesn't punish stuff well if it's without t-wave and can't hit it super-effectively with Psychic.
Again, I really don't like this reasoning. T-wave essentially cripples 2 of these mons and coverage with things like Knock Off and Energy Ball, both of which are viable on the defensive sets, also dent/cripple these mons too, and considering that scouting for coverage essentially could be a coin toss makes it harder to deal with. If you always knew what coverage it was, or know from experience vs a specific opponent what it's running, then yes, it's easier to switch-in to and check/counter; but in a blind game vs a team that you haven't faced, you can't say that you'd switch something like Klinklang in without scouting for its coverage prior.
Well single handedly it's not mesprit that causes pursuit to be such a big thing, because musharna, xatu, rotom, jynx, anything physically weak that can be outsped and finished off with pursuit basically is a reason to use pursuit and why it's such a huge importance in the tier. I can understand your pov whereby you think it's skill-less building because of how easy mesprit fits onto many teams, but at the same time i don't think that mesprit is suspect worthy.
Wanted to talk about what
Teddeh said too. Pursuit has risen in popularity recently, yes, but given that only 2 mons can use it effectively being Liepard and Skuntank, I don't think Tauros uses it effectively fyi because its other coverage is way less situtational and far more valuable, means that its usability is limited. The fact that the defensive set can get away for almost free with Colbur and heavily dent Liepard in the process, I find the fact that the offensive sets, Specs for example, forces a coin flip on both Liepard and Skuntank meaning it has the abilty to get away scotfree.
Finally, again I'm not saying it's broken, but the only set that I would ever consider it being broken with, is the Choice Specs set. Immediate power with great coverage and few reliable switch-ins essentially make it the most deadly set that Mesprit can run, with the answer to it being revenge killing or having a dedicated counter, Bronzor for example (which can be beaten with potential coverage), making it harder to build against.
I would however be interested in what others think about Mesprit's place in the tier and if it's overbearing in their minds n_n