I think it's badly designed.
But ofc that depends on your playstyle. Like if you are "casually" playing through the game, and are not looking for challenging fights to beat, then you will probably not have any issue.
But the issue is that the game is very much designed around a feature called "bravado", which is that you refill your action points on a killing blow.
Example: You have one character which does 5 damage, and you got 5 snipers with 5 hitpoints.
In this game, you will be able to spend 1 AP to get into position to shoot at the first sniper with 90% hit chance. You kill him. The kill refills your AP. Now you go to the second, kill him. This Refills your HP and so on.
Thats all nice. But you can guess what happens if you miss a shot. Yeah, you die. Because you are liekly now in a bad position and all 5 snipers will shot at you.
Now you might say "ok, I just be careful and only kill one per turn". However the game only has 3 difficulties.
And the Upper difficulty actually as a time limitation. So Assume in the example above that you only got 1 turn to kill them all. Yeah, in some missions you actually need to do pretty much perfect.
Any bad luck would mean you need to reload. And ofc chances accumulate.
And you can see from my example that in this case you wouldnt be able to compensate with any great tactical decision. In this example it would be down to pure luck / savescum at the point where it matters.