I did a handful of March of the Tortodrones runs back in the day before my several-year hiatus, but I didn't remember much about the event when starting it this time, and after going through a few rounds with a friend I have some...thoughts about it:

• First off, I don't mind having to collect glyphs from fiends to craft the ID cards. There are enough different ways to do it, whether it's grinding a particular mission or hitting a good gate in the Clockworks. I also like how you can get special glyph-rewarding themed rooms in Devilish Drudgery levels and Arenas, so it's not just constantly hunting for Clockworks Tunnels levels like most events. I'd like to see that applied to other events too.
• What I really mind is the cost in crowns. I'm sorry, but paying 10k for a single ID card that gates a mission that takes just a few minutes is kind of insane. That's like buying a single 4-star recipe for every run, or nearly 300 energy at the current exchange prices! I don't really understand the purpose of it either; there isn't any other recurring event that has that steep of a barrier to entry.
• The mission itself is pretty underwhelming, given that it's just a single battle room with only two enemies that you need to kill to finish it. Again, that hardly feels worth such a steep entry cost. You'd think there'd at least be some sort of warm-up level, maybe a Devilish Drudgery or something. That'd give players the chance to grab health/remedy capsules and vitapods before the Tortodrone fight, and maybe even score a few glyphs to make up for the ones spent on the ID card.
• The Tortodrone fight itself feels really overtuned, even on Normal difficulty. My friend and I tried it on Elite once, and I think I had to burn four Sparks in a single run. (Yay sunk cost fallacy!) We've done a few runs on Normal since, and I've yet to get through one without using at least one Spark. Usually I'm very good at staying out of danger, but there's just too much going on to keep track of. The Tortodrones themselves can dash halfway across the arena and hit like a truck, and it's very easy to get blanketed by their spke attacks and completely stunlocked. Meanwhile you have Overtimers darting all over the place hitting trident shots from downtown because you're too distracted by the Tortodrones to track them. It sucks having to run on Normal, because that nerfs the material drops, but the alternative is going through Sparks like candy. I know that Grinchlin Assault is pretty nightmarish itself, but at least that's mostly for alternate reskins of existing weapons (plus some hyper-rare trinket most players won't bother with). But the Tortodrones gate two entire unique lines of weapons, and it feels like a hard sell for the majority of the playerbase to have any access to them without burning a whole bunch of Sparks.
• And speaking of the weapons, I won't rehash a lot of the excellent posts about balance tweaks that have been made recently, but the rewards from this don't really feel worth it other than for swag. Here, have a line of shields whose only real unique attribute is a special bash attack you'll probably never use, oh and they slow down your movement speed too. And here's a gun line with questionably-useful charge attacks and abysmal range. Have fun!

So what would I suggest? Above all else, significantly reduce or even eliminate the crown cost of making an ID card. Tone down the damage that Tortodrones do, at least on lower difficulty levels. Ideally add a bit of additional substance to the mission. I'll leave the weapons balance suggestions to people who know what they're talking about.