Can Confirm Solo on DRK/RDM took 30ish mins.. the Fast cast is very dangerous but the magic range is 23.5yalms away granted you have no links! Happy hunting :3
Fairly easy NM to solo, does not take long and high drop rate on Scythe. Killed it 3 times in a row with 2 scythe drops. Solo on Lv.80 SCH with Cryohelix, poison and Bio II, took about 35min. The adds can make it suck and are more a problem then "Megamaw Mikey" but if you have some time, try waiting for it to move b4 you claim. Can get it in a spot where nothing will link and it will never cast a spell on you.
To be clear, it's no longer possible to stand out of range of Mikey and cast without being casted on.
It's still an easy solo with the right approach, however. Max casting range for Mikey is, as with other worms, 30 yalms. Max casting range to cast on Mikey is 23.5 yalms (possibly ~24 if Mikey is downhill). Simply cast on Mikey from ~23.5 and if he casts, DO NOT wait for spell to finish and run to 30+ IMMEDIATELY. He casts quickly, but you'll only get caught if he casts while you're casting and you finish the spell. He often waits between casts, however, making Tier IV nukes possible.
I advise /RDM over /NIN where possible, as Stonega III is faster than Stone V and will wipe shadows. Stoneskin, Cure III, Barstone, and Shell II are valuable assets. I had one Stonega III that didn't even break Stoneskin on BLM/RDM, and most others did little damage. SCH, BLM, and RDM will get the job done the fastest.
Me and my friend duo this nm me as Rdm/Nin and him as Drk/Nin, pretty simple only the links are a issue, make sure to keep him claim or else he will have a chance to go underground and regain to 100%.
If you use this with a platinum grip (I've only tried NQ, but I'm assuming HQ works as well), you'll cancel the darkness damage completely, and not just on hits the stun procs. This is nice for anytime you're subbing DNC (or just want samba), as it lets you get hp/mp/haste from sambas.