Guess I'll throw my own two cents in.
For me, personally, a lot of my leaving came down to bad timing and fatigue. Heroica is a lot of work to run, and even if I stepped back and tried to just be a player (which I honestly felt guilty about due to the lack of quests), that took a lot of work, too, between trying to juggle compelling story and character development with not hijacking the QM's quest AND maintaining mechanical competence (which in retrospect was most definitely not helped by my minmaxing, oops :blush:). It got to a point where playing the game felt like work AND never really paid off anymore, and at that point why play?
To go into a few more specifics, update speed was a HUGE problem on both sides of the coin. For players, it's infuriating--in this kind of system, you can do pretty much nothing without the QM hopping in to respond, and QM response times were globally getting longer and longer and longer. Back in the day, we as players managed to fill that blank space with compelling character interaction, but after six years most of the surviving characters knew pretty much everything there was to know about each other, or if the characters didn't we as players did and were running out of new ways to re-explore those same character components in interesting ways with new character combinations. On the QM side, however, it's incredibly stressful to try and build enough content fast enough to satisfy a party of ravenous players, particularly ones as meaty and plot-throwing as ours tended to be. Most notably, the requirement to provide visual sets made it very hard to improvise, even when we genuinely liked the direction the players are taking our plot and would like to rework.
There was also some bad timing in terms of story events that hit me in particular way too hard. I think the phrase "2016 sucked" and a vague gesture at the faction event is all that needs to be said on that subject.
If I were to offer suggestions--well, I offered a few in private at the time, but it's been almost a year since I've been around (and definitely more than a year since I've been invested), so my perspective may have shifted.
1.) More generic sets. Hear me out, one of the things that tore me apart when I was working on my planed duology was how few set images were reusable. I combed through the Baltarok trilogy looking for pics that only showed scenery and possibly a few generic NPCs, but the vast majority included characters who would be either not present in my own Quest or even worse outright dead. While the photography of the characters in those scenes was amazing and cinematic and definitely improved the storytelling of the trilogy, it also left me up a creek for trying to revisit those locations and recreate those sets; even just a dedicated set of "sets only" pics uploaded to the wiki after the Quest's conclusion would have helped me so much as a QM who's not good at setbuilding.
2.) Deliberate plot hooks left to other QMs. While I greatly appreciate the respect we all showed each other in terms of not messing with each other's plots and characters and ideas without permission, unfortunately I don't think we did enough asking, so as a result when a QM left or went on hiatus in between Quests, there were tons of dangling plot hooks and characters and stories left completely hanging outside of the odd non-consequential cameo. The best example of this is Sandy; we all used his characters and settings as springboards for our own, but it wasn't until near the end of the game that he started handing out "major" developments to other QMs, and so once he left we were all left with...basically nothing, because no one was willing to risk trying to build off of those only to produce an inferior successor. I think if we as QMs had more consciously created plot threads and then deliberately handed them off to our peers to develop and share back with us, it would have created a much better environment for being able to handle absences and hiatuses, where if one person vanishes (as is wont to happen on the internet), another is there to pick up the slack. Heck, even just having collaborations of multiple QMs on a single Quest would work wonders in reducing the QM workload.
3.) QM rewards. Plain and simple, QMing is a ton of work for little real benefit other than admiration and praise for the art you've produced. The one quantifiable QM reward, a second character slot, is literally just more work piled on top for you to deal with (see: playing is hard work too). That's not a viable system; implementing some sort of rewards program, allowing QMs' PCs to advance even just somewhat while they're too busy QM-ing to play, would go a long way towards freeing up QMs to QM. (Pathfinder and D&D both do this with their organized play programs, and to great success from what I can tell, so it's definitely possible to do without overdoing it.)
4.) Character slots. I get why we were limited to a single character at first. It didn't really work out. The permanence and finality of such a limit made even considering making a new character a huge burden to consider, having to weigh the risks of future potential for a character versus the fatigue you have from writing them continuously for half a freaking decade with no break. Have I really squeezed the last ounce of blood from this stone? Is a future Quest going to pop up where I'm going to regret no longer having my original character to play for a returning relationship? How annoying and tedious is it going to be to build up a new character to even a fraction of the mechanical playability I have now? Is this idea for a new character even going to be worth playing in a couple of months, or am I just trying to blow off creative steam while I try to get over character 1's writer's block--oh wait, shoot, character 1 is gone now even though playing this new character gave me a ton of ideas for my first one, oh well, guess I'm boned. For a sequel I'd suggest at least two characters per player to start, possibly up to four. Still have a max cap (I'd say no more than six even with expansions), and still have that cap expand with progression (so maybe start with one slot and then earn a new one every ten levels?), but let players have room to try something different; this might also help deal with the way that power tended to concentrate in the hands of a few key characters (*cough*Arthur*cough*) since now players will want to distribute some of those absurd spoils across their roster and, because of their diverse roster, will now have a diversified set of mechanical interests to be on the hunt for.
5.) "Day Zero" sessions. This is sort of a weird thing to suggest, and not exactly the most practical thing for the format used here, but remember how awesome Zepher and Endgame quests were in terms of grabbing players' plot hooks and hooking them directly into the Quest's own plot? Having a dedicated period of time between Hall departure and Quest start to work stuff like that out would be awesome, and doing it early would help give QMs/QM teams more time to adjust future plans to make use of them.
6.) Roleplaying sections in the character profile blocks. I know, weird suggestion, but it would work wonders in indicating to players that the game is about roleplaying just as much as it is stats and inventory management. (Personally I'm also a fan of 5e's flaws and motives system and how it grants mechanical advantage to good roleplaying, but I'm not sure it would function properly in this environment.)
All right, that's everything that was big enough it managed to stick with me even after deliberately (mostly) ignoring Heroica for nearly a year. Now let me go find my old complaints and see if I still agree with them.
(*Reads PM* ...oh cute, I was still presenting as male. Lemme just fix that... xD)
I guess the only thing I'd add after this is a personal failing as a QM. For all the Quest ideas and plans I had built up, I tried really, really hard to keep things a surprise from even my fellow QMs because I wanted to take their PCs on Quests and show off what cool things I could do. The problem that comes from that, of course, is that I ended up cutting myself off from a lot of advice and support that could have reduced the strain of QM-ing. In the RPGs I've played since, I've found that we've been a lot more chill about respecting spoilers and sort of working together to build up for big payoffs, and I think if I'd been a little more open in my plotting with the folks here, I might not have burned out quite so badly. I still don't think I would have avoided the burnout entirely, or even have managed to push out the Quest I was working on (I'll happily spill all the details in the QM Lounge at some point if enough folks are interested), but I think my leaving might have been on happier terms.
If folks want to pick up my plot threads to use in the finale, I've already passed "ownership" of Arthur as an NPC on to Zepher, and since Endgame seems to be around I'll go ahead and publicly hand Miirym to him. Diana belongs to KotZ now (or WBD if you'd rather keep potential for Kiray-Diana interaction), and I think with that all the characters of mine who had any significant potential now have new homes. Best of luck with the finale, and do drop me a PM once it starts--I'll happily read along in silence, even if I'm no longer actively participating.
P.S. still hate the new post editor, playing RotR in the old editor on BZP has spoiled me. xD