Experience will play a large role in combating these concerns.
I was on the same wavelength at first… but lowered my head and trained myself to recognize.
There is always a way to take down each merc… you just have to realize who you’re about to battle and how your merc can easily take down their merc.
Szakalot is right… it will come with time.
EDIT: Also… make sure you have a balanced loadout of mercs ready to go and constantly merc-swap to help with whatever stage your on and whatever enemies are out there…
switching from Merc#1 to Merc#2 can change your success rate in the right circumstances… you just have to play enough to recognize when that time is.