Put simply, it’s not (just) OP combos/exploits, it’s a balance and gaming experience issue.
I’m a new player, playing the game the way it tells me to play it. I don’t open the console to input a cheat command, I don’t go looking online for an unlikely combination of actions that lead to an unpredictable result (I don’t know, something like move 3 tiles forward and 2 tiles back, and one to the left and all the enemies drop dead).
The game encourages me to try different skill combinations, to stack buffs to accuracy and damage for better effect. I do just that. Thirty hours in, the game is completely broken: no matter the difficulty level, any number of enemies of any stats can be dispatched in a few turns. There is no challenge anywhere to be seen.
If you read the forum, you will see that this is a fairly common experience. After that it goes two ways - some players quit playing, others start playing-testing with self imposed restrictions, and give feedback.
A huge part of the problem is that it’s not at all obvious what constitutes an OP combo that will break your gaming experience. For example, what damage per AP is excessive and should be avoided? How much movement per turn is too much? How many enemies dispatched by a single soldier?
And this is not going into the other side of the equation - which is that many players don’t want a fantasy power trip, but they find the game too hard if they don’t resort to these OP combos. What they want is a reasonable tactical challenge for their skill level.
So no, this is not like playing a table-top skirmish game with a friend where you both know that such or such faction/character/tactic break the game and you agree not to make use of it. This is you and your friend playing a new game and suddenly, what, did you just wipe my whole team before I had a chance to move? Did we read the rules right? Then you spent 3 hours changing the rules and trying again. Well, that’s slightly better, but didn’t do it either…
Which is what you see happening here. The game is in much better shape since release for all players, but there is still a long way to go.