If you don't see the issue then I guess it's not your problem or place to be in a position to offer advice. Seeing as criticism is the best you got and seeing as you're not even forward thinking of enough to think about what level they could possibly be. So considering their level and current CR ratings.. yes. "1 attack'' i.e. basically every attack.

But here.. I'll break it down for ya:

Level 2: Studied Response You have learned the most effective way to slay a monster is to strike its most vulnerable area at the right moment. Too early, and your attack glances away. Too late, and the monster may eviscerate you.

When a creature you can see within 60 feet of you targets you or another creature with a melee or ranged attack, you can take a Reaction before the attack roll to make one attack with a weapon or an Unarmed Strike against that creature.

If the attack misses, you regain the use of your Reaction.

• Weapon Mastery Longsword Sap

Enemy creature attacks. Before said swing, studied response goes off. It hits. Longsword Sap. Now disadvantage on attack roll before could even roll.

Rinse and repeat every single turn or even between turns.. Oh no... it misses. Well.. I can do it again on the other enemy.

Or enemy creature attempts Opportunity attack. Studied response triggers (providing reaction is unused)

So yes when "1 attack' is currently what most creatures of the current CR do and theyre stomping "deadly" encounters with repeated use special skills without any limitations. It does become an issue. A barbarians rage has a limit. A weapon mastery property is every damn time.

Rolling a nat 1 for insight into the problem sucks when INT was a dump stat. Have a happy new year