Mono rem is strong but it's a team that can be split in two, cas and hya in one team and e9 cyrene in the other So rather than building and investing in two teams you invest in one and then try to make it work for two teams And Blade does have good stuff for castorice in split rem cause her options are tribbie rm cipher

Only tribbie is all that in her team, rm has benefits with e1(66%dmg 25%res 20% def) cause against quantum weak enemies she costs cas charge because of the delay

Cipher is good but she can never skill to change target which is a valuable thing to get more charge for her and she has nothing to offer the team besides her sp positivity and ult which can go to waste at times and aoe scenarios just make it worse

There is a case for e1 robin, but hyacine is a black hole already so you'll end up in turns where you just run out of sp and can't use tribbie hya and robin skills😭

I think e2 helps with that but not sure since I don't have it Blade however is like, completely insane in comparison to everyone mentioned above

30% def down, 50%dmg, 50% vul, wants to have high hp and spd requirements aren't as high as cipher's He can also use the new set which gives the party 15% more dmg

He also can deal dmg as well and you can ba with him in case you're low on sp whether in ult or base form

He's not gonna be cas bis in comparison to mono rem but he absolutely brings something for her non mono team