It is an example of one location. But what about Valley of Tears, Hell's Ridge or Embalmed Forest?
I am trying to look globally:
Is it OP against most dangerous challenges? No.
Is it OP against all enemies? No.
Is it useful in any location? No.
I think if we will make these buffs weaker then it became unattractive to level up during leveling. You can comfortably kill regular enemies with other ways. Archers mostly dangerous on initial levels. And not much enemies at all that uses spells.
Maybe good solution for both opinions is change % chance of deflection. Just for example, fixed 50% (or 33% +0,1% per level). But it's not about easy values changing, need to rewrite code of deflection value progression.
You forget that buffs may be used on allies. Sacred allows to play not only solo, but also in party up to 16 players. With your example you still have 85 sec cooldown at level 255 (not high cooldown reduction, but also no bonuses to these Combat Arts from items). With 85 sec cooldown it will be enough only for one ally and yourself. But most importantly is you need a good timing for buffing. If with such cooldown you want constantly use these buffs on yourself and on your ally, then you need to use it every 90 sec. If you made small delay, for example 20 sec, then for about 20 sec you got time window of not having these buffs on you and on your ally. Such hard timing is difficult and uncomfortable.
For real character cooldowns would be lower, but player also may want to use it not only for one ally, right? And also player can't support hardtiming of buffs during all game session, so need some reserve of time. So, even with 25 sec cooldown (about 1k cooldown reduction) you could comfortably support these buffs only for 4 or maybe 5 players. Also don't forget that casting buffs every 25 sec on different targets would become annoying pretty fast.
Our balance concept assumes the use of buffs on allies. If our concept assumed that you need choose to use buff either on yourself or on an ally, then we would made cooldowns a lot higher.
We also get feedback in private format and a lot of russian feedback. If you don't see it this does not means it not exist or it small.
And again this song.
A lot changes already made since you tried Dwarf 2-hander: reduced bosses health, buffed some enemies of Ancaria, implemented possibilities to get proper damage types.
I think currently playing Ancaria campaign on silver is extra comfortable and almost no difficulties for experienced player like me. So for usual player Ancaria campaign on silver should be interesting to play or at least comfortable.
I promise you that once I will made an stream sessions with Dwarf 2-hander completing both campaigns in solo mode . But all my commentaries during stream will be in russian.