So Maelstrom Missions are one of the mission option sets within the 7th Edition 40K Rulebook.
I won't rehash the overall discussion about what constitutes 7th Edition as a whole here ... it's really hard to accurately / adequately answer. I stand well into the camp of 7th Edition being the DIY Edition - it's really about setting your preferred parameters and making sure you find people to play with who follow similar ones themselves.
There are definitely purists who will argue that Maelstrom Missions should be included in a Tournament Packet "Because it's part of the game." Most of those same purists will argue AGAINST the inclusion of some part of the rest of the game anyway, so it's hard to give that argument any meaningful credence.
Instead of digging into whether or not it should or should not be included, I thought it a worthwhile endeavor to articulate why I'm not a huge fan of them.
So, the rest of this is quite opinionated!
First off - stop calling it a sign of a good tactician that you can handle Maelstrom. It isn't (which isn't to say there are 0 skills involved, stay with me). Building your list as capable of reacting in the moment to an objective being randomly determined that says "go do this thing, right now, go go go" isn't the same as being a good tactician. There's very little tactics involved with Maelstrom. They tell you to do something, immediately, and even in modified versions of the Maelstrom you have almost no control over what it is you're being told to do, and what your opponent is being told to do. Following / executing Maelstrom missions is equivalent to fulfilling "collect X of Y" quests in Role Playing Games. The equivalent of an NPC generates them, and you have no real say in what they are.
Even in highly modified Maelstrom missions like those seen in some of the major tournament packets, oftentimes it simply is a matter of "did I pull a Maelstrom that is easy to accomplish, difficult to accomplish, impossible (or effectively impossible) to accomplish, or automatic to accomplish?" Games are routinely won and lost on the random pull of Maelstrom missions. Even in situations where they take a secondary role, getting dumb luck on Maelstrom early on and gaining an insurmountable lead gives the person who got lucky in such a way great incentive to simply push for a tie on the superseding Primary.
It's hard to say that Maelstrom missions represent "bad" mission design. It's hard to say this because you don't know what the intent of the designers was. If the intent was to have tactically demanding, interesting missions, they are objectively abject failures. If the intent was to have zany things happen and the outcome of a game be often irrelevant when playing by-the-book Maelstrom ... well, great success!
There are less ad-hominemy ways to refer to them, especially when talking about modified Maelstrom missions such as those seen in ETC and Frontline mission formats. I'm still not a huge fan personally - I've seen too many playtest games and live tournament games using them determined by randomization, which is something I'm not a big fan of. That said, they are undoubtedly MILES ahead of what GW put out in terms of being reasonable for tournament play, and they largely (and rightly) take a backseat to more tactically challenging / strategically-demanding primaries (so Kudos on those guys who designed the modified ones!).
There's no major point to this - just thought it might be valuable to share my personal feelings about Maelstrom. Fortunately, one of the nice things about the game is that it really lends itself to a wide variety of playstyles, missions, point levels, regulations, etc. - by virtue of the fact there really isn't one "way" to play the game. Fortunate for me, as I prefer the missions in my strategy games to be strategic ones :) ... where the ultimate path to completing a meta-objective or set of objectives is up to your careful plans and execution ... as opposed to not really having any idea what the meta-objective is until PRIVATE, GO CAPTURE THAT, RIGHT NOW! Hence my feeling that it's more of an RPG or even "action adventure" element to an otherwise-strategic/tactical wargame. Not my personal best fun, but not to say it can't be fun for others :) ... there's a reason there are plenty of folks who enjoy RPGs and action adventure games. They're just not my personal fave.
On Maelstrom thoughts, /fin ...
This is one of the interesting subjects related to 7th Edition Warhammer 40,000 and what the game is today. It's almost as if GW took one step further on the road they were on and said "screw it all, we're just going to release rules and we'll see where everything drops ... just don't use what you don't like." The proof is, as always, in the pudding with this as well. Zero events use the fully unbridled event rules, even an event like Mechanicon that claimed to be the only "true" 7th Edition Tournament refused to use Unbound army construction rules (thereby instantly becoming no more "true" 7th Edition than any other event).
To be a true 7th Edition Warhammer 40,000 event, frankly, you'd have to simply allow players to randomly determine a mission and a play format at their tables through discussion (which would, of course, end really badly). The "unbound" (pun intended) game is entirely impractical at a tournament level by simple virtue of the fact it's so very irregular.
The flipside and upside of all this is that GW has produced a game which is no good for random player encounters out in the wilderness of local game shops ... but which is fantastic for Organized Play and established gaming groups. If you have either an organizer who can establish the ground rules for what "style" of 40k you'll play or an agreed-upon format within your social grouping, you've got a game that everyone participating is more or less cool with, and that everyone can participate in with less confusion and concern about what they're exactly getting themselves into.