MCrit gear is currently capped at +30 MAB (+40 MAB total including base), so the maximum value of 1% Mcrit rate on average is +0.4 MAB:
https://www.bg-wiki.com/bg/Magic_Critical_Hit
Maximum value for +1 MCrit damage is "MCrit rate" MAB. So if you have a 30% MCrit rate, +1 MCrit damage gives you +0.30 MAB on average. With a 100% MCrit rate, +1 MCrit damage would be +1 MAB.
MCrit gear:
Wise Strap : MCrit Rate +3%
Wizzan Grip : INT+3
Maniacus Sash - 10% MCrit, 7 MAB, -10 MAcc
Othilia Sash - 6 MAB ?
A'as Circlet - 10% MCrit, 6 MAB, 5 INT
Nares Cap - 5% MCrit, 5 MAB, 12 INT, Set Bonus
Goetia Gloves +2 - 5% MCrit, 5 MCrit Damage, 7 INT, 8 MAB, Set Bonus
Nares Cuffs - 13 MAB, Set bonus
Hecate's Earring - 3% MCrit, 6 MAB
Novio Earring - 7 MAB
Choleric Earring - 10% MCrit, 10 MCrit damage
Genesis Locket - 5 MAB, likely 5 MCrit damage
Stoicheon Pendant - 8 MAB, 2 MAcc?
Using all the MCrit damage gear available (likely MCrit damage +20), Hecate's (3% MCrit rate) is still only worth +0.9 MAB on average, making it worse than Novio. Similarly, Wise Strap is always worse than Wizzan Grip.
Genesis Locket would need a 60% MCrit rate to be better than Stoicheon Pendant. Not reasonable, so we can nix it.
Chloeric would have to give more than ~6.6 MAB (Hecate's without Choleric) to be superior to using Hecate's. Using full MCrit damage gear (+15 for 25 total now that we're ignoring Genesis Locket), you would need a 27% MCrit rate for that to work out. This will only be work out if it's also worth using Goetia Gloves +2 or A'as Circlet.
A'as Circlet needs about +40 MCrit damage in gear to be better than a set-bonus-less Nares. This is not possible until SE increases the cap on MCrit damage.
It's alllmost close, but no cigar. They need to adjust something substantial or continue to add even better gear so that the MCrit system is worth using. If Nares cap had 0% MCrit and Genesis locket was better, MCrit builds would be the best option.