I ended up being potentially over levelled for most of chapter 5 and 6 because I managed to get enough Merc points to get the second side quest which requires beating two Lv44 drivers that kicked my ass until I was Lv48, but I refused to play further until I had finished that battle because I wasn't sure if it would count the exp I got from merc missions since the counter just hard stops at 2000 or w/e it was. It turns out it does, so I was worried for nothing.
The rest of the game was fine, I started getting the hang of Blade Combo's by Chapter 3 when I got Vandham since wind is a very good element for the Fire/Water/Earth that the main crew provided. I also got Finch which gave me a wind Blade of my own. I spent most of the game with Rex(DPS), Nia(Full Healer) and Tora(Tank). I also spent most of the game using exclusively Pyra/Mythra on Rex since I just never got a blade I liked for him until Praxis, because lances are like the only atk type weapon that isn't slow as fuck. I wasted Wulfric on Zeke.
Upon getting Nia as a blade, I decided I needed to rethink my team because I really wanted to use her as a blade, fortunately she's good enough to be the healer for the entire team while only using up one slot. Morag became my main tank by boosting her agility to absurd amounts and giving her Aegeaon and Theory, who further boost her agility and have decent block rates for attacks that don't miss. Tora stayed on the team thanks to Poppi QTPi, who made him into a half DPS, half tank that could sponge a lot of hits thanks to his high HP but could deal out respectable damage. Also QTPi had access to Launch, which was the only thing I was really missing so I could finally pull off proper Driver and Fusion combo's without just getting lucky and/or settling for Topple. Mythra's recharge ability also had gotten to max at this point so I could just spam arts at 50% crit rate, with an accessory to recover health for each crit to make Rex into a self-sustainable train of damage. The only problem was that Tora just would. not. stop. using. QTPi. Even when the blade combo was ready for him to finish, he would never switch off her because he prioritised Driver combo's and she has both Break and Launch.
I ended up with Rex (Mythra/Puren/Nia), Tora (Alpha/QT/Pi), Morag (Brighid/Aegeaon/Theory), with Zeke on the bench with maxed out luck accessories for pulling blades. I ended up having like 27 Rare Cores, 80 Commons and 5 Legendaries in my inventory for the final boss since I had no reason to keep pulling at that point, I had little interest in changing my party configuration that late.
Also I have to mention how much of a god send ascended Mythra is, I went from only being able to create 5 orbs (at Tora's mercy) to being able to make 7 (8 if I'm incredibly lucky) and being able to make up for the AI's mistakes at any moment. I never once needed to go over 5 orbs for anything in the main story anyway, I only ever needed 5 orbs once too, you could land a Full Burst off 4 if you enter the chain attack with ascended Mythra. I actually fucked up the last chain attack on the final boss trying to be fancy, though I could have killed it off 3 orbs I just was just trying to do something interesting for the end since the boss itself was easy, literally just spammed while morag tanked. not sure what tora was doing, moral support?