Kudos! Be sure to share when available.

Wish I knew

Here it is:
https://sins-of-the-sun.github.io/warlock-ias-calc/


Now you know

Awesome! Thank you

For a bow lock using mirrored blades, what is the best mist base? Colossus Crossbow or Demon?
Using Hex Bane (not purge) and Lvl 12 Fanat from a Bound Demon
Seems you don't even need ias on gear for max frames on demon and cap out on max colossus frames with 40ias? Is that right?

This is how I would build it:
https://maxroll.gg/d2/d2planner/h8b1ds0h

nevermind maxroll, it's reaching max speed, 12 fpa for both cleave and mirrored blades
using a +4 rangeadder WP

The overall dmg is pretty much half n half magic/phys
I made 2 sheets, one with magic sunder/jwl/opalvein, the other with the phys ones, but it could be a mix of both
Last sheet is 125fcr, magic oriented (no indestructible weapon tho, but still 12fpa with +4 range)

Using demon xbow and lvl 15+ mirrored blades, you only need 10ias
Easy to get from gear, probably already have it just from hellwarden or mist, so you don't even need fana... you could replace fana by a HF+cursed demon

https://sins-of-the-sun.github.io/warlock-ias-calc/?skill=mirroredBlades&skillLevel=15&ias=0&hexPurge=0&fanaticism=0&markOfTheBear=0&burstOfSpeed=0&holyFreeze=0&decrepify=0&chilled=0&slowPercent=0&weapon=Demon+Crossbow+%5B-60%5D&weaponName=Demon+Crossbow&wsm=-60

If you want it more phys dmg oriented, you could use a colossus xbow + fana demon
needs 80 ias in this case
mist + hellwarden + HL + gloves
or just an up'd Buriza (already comes with 80ias, 100% pierce)

https://sins-of-the-sun.github.io/warlock-ias-calc/?skill=mirroredBlades&skillLevel=15&ias=0&hexPurge=0&fanaticism=31&markOfTheBear=0&burstOfSpeed=0&holyFreeze=0&decrepify=0&chilled=0&slowPercent=0&weapon=Colossus+Crossbow+%5B10%5D&weaponName=Colossus+Crossbow&wsm=10

Is a magic sunder better than a physical one? Even if I use bane instead of purge? (hex)

Nice, yep... trying to squeeze out an enigma mist/buriza/demon machine + razortail build that has 125 fcr

it will be hard to reach your ias breakpoints if you use bane instead of purge
unless you use a fast base, in which case you prob just sacrifice both phys and magic dmg at the same time