General

@hualicious: There's no better card to replace MM if you don't have 100% Crit rate.
The only essential character cards are:

DA, Kanna, BT
Hayato, 2 empty slots
Mechanic, Shade, filler 3rd Pirate card for 6% IED (Xenon/AB/Jett/Captain)

No other cards give min/max critical in GMS, so you're already maxed out there.
3 Thief set is extremely wasteful considering you don't even have a thief in this set of 7 essential cards.
Blaster is a possibility for an empty slot, and the MM would fill it in. Replace Blaster with Zero for leveling.

Demon Slayer is irrelevant in a few months.
Mercedes is useless for Mercedes herself because it doesn't apply to most of her skills as they have

@akon1659: Look at the top

should i just reroll my IA?
Mercedes Forum Talk about Mercedes

@hualicious: Yes you should include it, It's one of the best character cards in the game and who said anything about a mercedes?

@akon1659: No, I shouldn't include Marksman card because Mercedes have 60% Critical Rate. So it's easy to get to 100% Critical Rate without using the MM card. And yes there are other cards that will benefit Mercedes.

My Mercedes has Min Crit 35% and Max Crit 80%, so it make more sense to use cards to increase these stats.

So Mercedes has Crit Chance 60%
+15% Phantom
+7% Beast Tamer
+10% decent SE
-----------------
92% rate already and there are still other resources to boost it up to 100% without the need of MM Card.

Combined with his current IA it will be 100% if he didn't reset it. But of course it is recommend to get a different IA on a Mercedes.

This also applies to a Night Lord with having 55% Critical Rate, it is not recommend (but of course optional) to use a MM card. On jobs with high critical rates you try to max it and try to raise as much as possible Min/Max Critical Dmg.

By using your available resources properly you can get 100% Critical Rate, 100% or more on Min Crit and Max Crit Dmg.

I've spent ATLEAST 5m honour trying to roll for 2nd line crit, keep it.

@hualicious: you should include the mm card, Having 100% crit will do more for you than any other char card.

Keep the critical rate 16% on the 2nd line of your IA for now.

Try to get critical rate stats from:
-Decent SE (Skill or Nebulite) 10%
-Phantom Link Lv2 15%
-Beast Tamer Link Lv2 7%
-Hyper Critical Rate (optional if you got points to spare, max is Lv10 15% but you don't need to max it if you don't have to)

I didn't include Marksman card because there are other better cards that you could use instead to boost other stats.

lock and reroll

Crit is great on second line, but ultimately you'll want to reroll it.

Mercedes can get 100% Crit with her skills + dSE + level 5 Crit Hyper Stat + BT/Phantom links at level 2 + S ranked MM card.

getting 16% crit rate 2nd line is pretty good (and rare?). i would lock 2nd line and reroll for better primary line instead of using circs.

imo i would farm and lock, but hey its your char. you do you.

my first lie of IA is 20% boss if that helps.