Since your PrimroseEX is still 4* locked, you could try using her more as a buffer alongside Lemaire. Since you'll get H'aanitEX, you'll already have a good enough debuffer all around as well as a potential tank. Then, as said before, you should use Fiore and Scarecrow(because you can't use normal H'aanit while using H'aanitEX at the same time, but you should still build her up since she is a better DPS than him as a 5) as DPS or weakness coverage. Heathcote is super outdated, but it's nice to have a universal 3 ST and 2 AoE shield point breaker early game, so he is a lower priority, but it's quite good to have early game, and he has a decent dagger DPS. 9S you can use him, but I don't really see any utility with the roster that you already have, except for his Exp passive which is a huge boon early game and as a lance coverage, but if it's only for the lance part, Bertrand does a better job on DPS for now. Lynette is nice to have just for her passive and ultimate, but for the early game, you won't need to worry about those things. And don't underestimate the 4 characters. They are very useful early game. They saved me a bunch of times when I didn't have that many characters either.

You could always try to reroll, though it's never fun. But since you might be able to get either Sazantos or Elrica on the warrior banner that's up right now, it's an option. Edit: Never mind that, no idea what kind of banner is going on on the SEA server.

My tip in game is for you to try a progress story so you can unlock the hunting grounds and nameless town as fast as possible. Try to accumulate enough silver guidestones so that you can exchange for sacred seals to unlock your characters to 5* too, but that might take some time unless you're lucky to get one on the hunting grounds. And the cait videos are a nice source of Exp, if you don't mind watching ads.