I’m not sure if these are little bugs, but there are two things that bother me. 
Ⅰ In Japanese (I’m not sure about other languages), the cause of death isn’t displayed on the death screen.
Ⅱ The issue of stuns on bosses making them attack more aggressively. 
I haven’t used stun builds recently, so I don’t know how it works for the bosses added in 1.2 and 1.3.
Personally, I like the current stun system itself, except for the two issues below.
Therefore, I’d rather see these boss attacks reworked than a rework like the introduction of a stun gauge.
The following content will use the detail tag as it slightly deviates from the main topic.
Other issues I've feeled with stunning to bosses are as follows:
- The boss stun duration is so short that Increased Stun duration seems almost useless against them.
Also, effects like "“Pummel and bash node (Werebaer)” that deal more damage to stunned enemies were almost meaningless against bosses. - It’s unfortunate that when bosses like Aberroth and Uber Abberoth deploy wards, the chance of stunning decreases, significantly reducing the return on my stun investment.
On the other hand, it essentially functions as a barrier for the enemy, which I also think is a good design. But I wish there was something…better.
Incidentally, if you're considering a stun gauge, I'd like to claim the following in advance:
"If I don’t invest enough for stuns, boss will be stunned around 2 times. If I invest enough, boss will be stunned around 5 times.”
This may be well-balanced, but personally I don’t think it’s much exciting if the investment results are like this. Of course, game balance is important, but I think it would be more exciting if the results were a little more extreme, like stunning the bosses 10 times or 20 times.