Started with Therion, and maybe I'm just a scrub, but Aeber's Reckoning is crazy good. I made sure to get him the Warrior's Surpassing Power and with Primrose on my main team buffing him he does 20k-25k to bosses and if random battles are going too long, i.e. if Primrose!Scholar doesn't flush them out, I just use Therion to mop things up.
I took way too long to get Alfyn (2nd to last of my ch1 runs), Concoct is broken and Rehabilitate granting status immunity is something I didn't realize I wanted in a status cleansing ability until now.
Running Therion!Merchant or Hunter as needed, Primrose!Scholar, Alfyn!Warrior or Cleric as needed. The forth slot as filler for completing chapters.
I used to run H'aanit, but Provoke is just too labor intensive to be worth it when Olberic exists; and Ophilia, but she is so underwhelming I may as well give Cleric to someone else, like Tressa, and not really lose anything, and Primrose overlaps her skill, with the best NPCs being worth the risk often enough. Having both Steal and Purchase at a time hasn't been a drag, if anything I often end up bringing Tressa when Steal doesn't get the job done (i.e. the 3%-8% or 0% rates). Scrutinize is so blatantly inferior to Inquire, as the failure chance isn't worth the risk unless it's for the weapons/armor stock, which there is no way to know in advance without a guide.