Minor update!
The arc is now fully 'I16-compatible' [custom mobs should give decent xp while not being too annoying to fight]. There were also two more reviews and a re-review; I edited them into the original post, but I'll list them here for posterity:
Re-review by GlaziusF on the COHMR page (or forum thread) -- 5 stars
Review by airhead -- 4 stars
Review by Coulomb2 on the 'Pro Payne' thread -- 5 stars
The arc is sitting at twenty-something plays atm (and was hit by an anonymous one-star bandit /sigh), so if anyone is looking for an arc to play, go ahead and give it a try! I'm also open to feedback and suggestions for improvement.
-- Z.
Another minor-ish update.
I fiddled around with the level caps a bit. With the addition of super-sidekicking, I figured lowering the cap to 45 would still allow level 45+ characters to gain full xp and use all of their powers, AND they wouldn't have to slog through endless crey tank spawns. It's a win-win I think, unless I missed something!
There was also one more review:
Review by Tangler -- 4.5 stars
The arc is sitting at 30 or so plays, and was briefly on page 3 in the 5-star zone before being voted down into 4-star-limbo again. Ah well. 
(an aside: is it acceptable to post ingame comments to an arc in an arc thread, and if so, should the @global names be anonymized?)
-- Z.
I've seen some posters post comments including globals with no complaints, but you can always just keep them as anonymous quotes if you want to be sure.
A Penny For Your Thoughts #348691 <- Dev's Choice'd by Dr. Aeon!
Submit your MA arc for review & my arcs thread
Yet another update.
After some deliberation, I removed the kill-all objective from the last mission and eased up on timed missions; I also reduced the number of objects that need to be destroyed in mission 3.
I also got one more review*:
Review by PoliceWoman -- 5 stars
I think I gathered enough feedback to stop making major changes to the arc at this point; I'll still be fixing bugs / typos / errors, but other than that it'll probably remain as it is now. I should probably get to work on something new!
I'd also like to thank everyone who reviewed the arc and/or left feedback, you made me want to keep going all this time. I'd also like to thank the Academy-- err, sorry, wrong speech. <3
-- Z.
* The arc was also featured in the 'AEntertainment Tonight' radio show, but I'm not exactly sure what rating I got overall; I know I got 4 stars from one of the reviewers, though
Arc Name: The Coldest of Wars
Arc ID: 299972
Faction: Heroic
Creator Global/Forum Name: @Celestial Nemesis
Difficulty Level: Moderate. Mostly stock enemies (Crey, Freakshow, Winter Horde), with a single spawn of custom villains in the second mission and an all-custom fourth mission. I've toned down the customs after playtesting with a low 20s villain group (note to self: tanker attack sets on lieutenants are a bad idea). Last mission has an EB, but it should downgrade into a manageable boss when playing solo on a low difficulty; its powerset was also altered to be less frustrating to solo players while still providing a good challenge. **NOTE** Two of the four missions are timed, but the timer is not too strict and there are appropriate 'branches' of the story if a timed mission is failed so that the story still makes sense. The sense of urgency is an integral part of pulp 60's spy movies, so I couldn't resist.
Synopsis: The Federal Bureau of Super-Powered Affairs keeps a close eye on Crey, trying to find evidence about a suspected illicit superhero engineering program. You assist agent Janet Kellum following a lead about a potential breakthrough, only to find that this time, Crey have bitten off way more than they can chew; their meddling has awakened an ancient, all-but-forgotten enemy. Can you stop this old-new menace before it's too late?
Estimated Time to Play: 45 mins - 1.5 hours, depending on difficulty, team makeup, etc. Of the 4 maps, the first is Medium, the second is Small, the third one is a smallish outdoor map; the fourth one is also Small, but with a kill-all objective. The last two missions are timed, but my low-damage test team was able to finish with 1/2 of the clock remaining.
As a solo lv42 rad/sonic defender on heroic difficulty, I completed the arc in 45 minutes, but I didn't spend any time reading descriptions or mission text. [NB: this was before I shortened the outdoor mission, it should be much faster to complete now]
Link to More Details or Feedback:
COHMR page, review by GlaziusF (now re-reviewed after I've made some improvements to the arc; original rating was 4 stars, the original review is also available on the COHMR page) -- 5 stars
Review by airhead -- 4 stars
Review by Coulomb2 -- 5 stars
Review by Tangler -- 4.5 stars
Review by PoliceWoman -- 5 stars
Notes: This is a story-focused mission arc; I tried to make its tone a bit campy (mad science! when ice cream licks back!), but not off-the-wall absurd either. I'm especially looking for feedback on the custom group on various difficulties / team sizes (too easy, too hard, too annoying, not annoying enough?) and general impressions about whether the story 'works' or not. English is not my native language, so any spelling / grammar / style corrections are welcome!
Mission note: I changed the #3 [outdoor] mission map after some review feedback (that I agree with) regarding the annoyance factor of large outdoor maps and annoying places for glowie spawn spots. Sadly the new map has unremovable civilians all over the place, running counter to the story -- just ignore 'em. I'll keep it as it is for now until AE gets a suitable smallish residential / commercial outdoor map that could work for a 'normal' neighborhood... imo it's better to have a less annoying map than a more immersive one. :P