I can safely say that Mega Camerupt isn't a broken Pokemon by any means. Whether or not it is good or bad is a different story, but I have seen little to no evidence that Mega Camerupt would be broken for NU. A lot of people have been talking about Trick Room but I haven't even bothered with that because even with Mega Camerupt and Slowking being better, Trick Room offense still isn't all that great, especially when you're facing playstyles other than offense. On top of that, I will agree that Mega Camerupt is probably more threatening defensively than it is offensively. Not that it isn't super strong, its just that oftentimes I find it hard to get in on the field to do heavy damage in a lot of match ups, especially since it has no recovery. Let's go more in depth with some of these negatives with a list:
- Low Speed
- Unreliable recovery
- Ground weakness
- Limiting building
To talk about the low Speed a bit, Mega Camerupt is super slow. It isn't Ferroseed slow, but it would be one of the slowest Pokemon if it dropped back into NU boasting Base 20 Speed. This is slower than even Slowking, and while it will probably not want to out speed Slowking in most situations simply for the fact that death will ensue if you leave it in, it is important to note as this goes in hand with the lack of recovery. Mega Camerupt being slow would be a lot less of a noticeable if Mega Camerupt got a move like Slack Off, perhaps. In a lot of match ups I find Mega Camerupt in, it would be incredibly helpful if it was able to recover off the damage it takes before it is able to get up Stealth Rock or perhaps launch off a powerful attack. Hell, most attacks Camerupt has been taking in my experience have done more than half anyway, but perhaps that isn't as big of an issue as I am making it out to be. Still, Mega Camerupt would actually do great with recovery if it were to stay away from super effective attacks, at least from what I gather.
Something I don't see many people talking about is the Ground-type weakness. I think that this is a pretty bad thing for Mega Camerupt, especially as a Stealth Rock user. It pretty much loses to Steelix and Rhydon. In the Steelix match up, you have to choose whether or not you want Stealth Rock or to break the Steelix's Sturdy, as Earthquake is doing over half to Mega Camerupt. While Steelix can always Stealth Rock, it is usually a better play for them to get the heavy damage off so as to not let Mega Camerupt in without repercussions to then fire off a deadly attack. (Druddigon is synonymous with Steelix in this example as well). For Rhydon, the same logic applies, except that Rhydon actually has a very high chance to OHKO Mega Camerupt. I feel as if Mega Camerupt didn't have a Ground-type weakness, it would have a much better match up as a Stealth Rock user.
Finally, something that I noticed in the literal first game I played with Mega Camerupt is how limiting Mega Camerupt is in building. Not in the way Vanilluxe was where it would limit the opposing builder, but in the fact that it limits YOU as a builder, sort of like Mega Abomasnow. I faced quziel on the ladder and we both had very similar teams. One of the reasons behind this is that Mega Camerupt isn't a flying resist (just to note, Seismitoad and Druddigon also share this problem, but its still important to note for Mega Camerupt as well). The two most common Stealth Rock users are Flying resists so that means you're going to have to run either Aerodactyl, Togedemaru, or Rotom for a consistent Flying resist, as Heliolisk isn't great defensively (although neither are Aerodactyl and Togedemaru, honestly). For Mega Camerupt, you'll also want a Water resist that won't have severe repercussions from facing Water-types. This is actually an easy task depending on the build route you take, but can be difficult in some scenarios, especially since most Water answers still struggle with Water-types in some capacity. Even though those two things don't seem that bad, they are kind of big in the builder when you don't want to build the same non-Trick Room Mega Camerupt team every time (or at least avoid similarities).
I haven't tried out defensive Mega Camerupt to discuss that front so perhaps I will edit this post with information on that in the future. EIther way, though, I don't think Mega Camerupt is broken by any means. Some people might argue that unbanning it would add an unhealthy Pokemon to the tier because of how it promotes Trick Room builds, but I don't see Trick Room becoming super prominent with the addition of Mega Camerupt. In fact (and I'm positive they exist), I haven't seen a Trick Room team yet with Mega Camerupt, or, if I have, it wasn't a notable build by any means. I think a week's time is definitely hard to gauge if Trick Room has become more popular or not as a playstyle because of Mega Camerupt, so I think having a suspect test would give more time to see if that would increase in usage. Overall, I see no harm in having at least a suspect test, and even in this less-than-a-week's time, I already know I would probably vote unban on Mega Camerupt.