It was overly active redraws - redrawing every element on the merc page every time credits updated as part of a check for if the player could afford to hire the merc. Limited the redraw to just the buy button and got smarter about how the check was happening (raising credits won't make an affordable merc unaffordable so no need to check sort of thing). A couple other pages had the same issue but weren't hitting the tipping point in elements where the slow down was obvious - yet. Tried to fix everywhere where it was happening as part of the last set of patches.
Viewing post in Update 0.45.0 - Missions and Merchants comments
Good to hear. That makes sense, seems consistent with where I had minor slowdowns in the before times pre de-cluttering update.
I'll dip back in to test things out every so often when I see there's been a new update, but my playthrough is at the point that I'm just twiddling my thumbs until that 3rd prestige layer gets implemented. Ping me if you want anything particular play tested on the phone browser side before then.