Should I Re-roll? Is this re-roll good?

Short answer is get at least one lucy or masamune. BUT, if you are willing to spend time re-rolling, get 2-3+ good units.

Long answer... MS unit evaluation and philosphy on how to pull banners is tricky and very subjective.

Either go to GW page GW re-roll ranking or the Discords #ms-guide (look for re-roll tier list) if you need names/pictures of units

Discord invite link: https://discord.gg/QWvbWAj

Get units from bad banners first philosophy:
I would vote getting 1 lucy first is preferred over 1 masamune.
Some people vote Lucy first, because her banner is bad (beginners should not pull, old 2015 banner, most units are bad).
AND... beginners should pull legends banner, so you will (probably) get masamune eventually.

Get high spec units first philosophy:
Going masamune first is also a great choice, because shes MUCH better at going to high difficulty quests than lucy. Masamune has a top tier kit, strong bump, strong abilities, strong strikeshot(SS).
Some background, she is the legends unit released on new years (January 1, 2024); while Lucy is a former legends NY unit from 2015, but her newest form was released 2023. NY units have some of the best kits.

Is two masamune good? Or lucy masamune? Or masamune anastasia? Or masamune+3 others?.. etc...?
Each unit is good at different things and have their own roles. I go into detail in next bolded section below.
As a new player, you first want unit thats good at general content, where strong bump combos are important. (Note high difficulty content, they tune the quests so direct damage, NOT bump combos, are the way to win.)
MS is played with 4 units in a team, and even one unit with strong bump combo is sufficient. The other 3 units in the team can have different roles and bump the unit with strong bump combo every turn. IE. having 2 or 3 lucy is a bit redundant.

To keep it simple, go to GW Tier list, and don't pay too much attention to the naming of S/A/B/C tiers. If you see a unit on this tier list, its either top tier in a particular quest, or very strong and use-able in particular quest. Looking at S/A/B tier, some of the units with more impressive kits are here versus C tier.
So all units are good, but C tier may be more niche and specific, but still good. Evaluate your re-roll based on how many units you have that are in the tier list. Or just ask on the discord.

Each unit is good at different things and have their own roles:
So masamune is MUCH better at going to high difficulty. If masamune sounds so great, why does anyone want Lucy?
MS is a game with a lot of unit/quest variety (gimmicks). Masamune will have some things and quests shes good at, and Lucy will have some things and quests shes good at.

This applies to ALMOST ALL MS UNITS, they all do different things, and if you stick around discord long enough people will hate on GW tier list because of this fact. Its not simple so say Unit 1 is S Tier and Unit 2 is C Tier.
This is like trying to ask whats better, a hammer, screwdriver, or wrench? It depends on the situation (quest), and you'd have to crawl over my dead body before you took those out of my toolbox (monster box).
GW has Masamune S tier, while Yakumo (2022 NY legends unit) is not. BUT, they are both EXTREMELY strong in the quests they belong in. (If you wanted to speculate, I think GW put masamune at S tier soley because her quest is one where the best hardcore players farm non-stop every month to get a rare spawn.)

I will say the MS devs put better kits on legends NY units. IE. they'll get abilities/bump combos/strikeshots no other monster has, they have MORE abilities than your average monster. So a Legends NY unit may be able to go to more quests because of this impressive kit. While a general pool (genpool) mon, may be designed to precisely counter one quest, and thus only strong in that one quest.
Every once in awhile a monster shows up in collab/alpha/element( and etc...) banner that rivals a legends/guardians.
Right now (as of 2025), the only genpool with a strong general use bump combo is Martha, otherwise the good genpool kits are very specific to counter a single quest.

For extra reading, can read GW talk about the game. Characteristics of characters you should draw
The article is old from 2022, but the general advice is sound. It recommends strong bump combo mons for low difficulty.
Corrections - Do not refer to their list of mons, this article is outdated with the list.
Corrections - It says gouzetsu is highest difficulty, but reizetsu is newer and higher difficulty. Gouzetsu ML can still be useful though.
Corrections - it shows uncharted lands, but this is obsolete and removed from monthly quests.

So all units do different things, MS devs do not really create exact copies of monsters, always subtle differences. Legends/guardians usually have impressive kits, but once in awhile you'll see an impressive kit in collab/alpha/element( and etc...) also.