What do you think of the following feat?
Advanced Combat Techniques (Fighter/Monk 8)
Whenever you make a disarm, grapple, reposition, shove, or trip attempt, you compare your roll to the lower of the target's Fortitude or Reflex DC to determine the results.
I would suggest making the player pick which save they want to target instead of automatically targeting the lowest one.
That way the feat introduces interesting decision making, and it becomes a chance for the Recall Knowledge character in the group to shine instead of something that makes them obsolete.
I considered it, but it also slows down the game, makes it dependent on a highly unreliable mechanic (and that's assuming the character or their allies even invested in and use RK), and unduly punishes the player using it when they guess wrong.
This way is faster, simpler, and always works well.
My only suggestion would be to lower the level to 6, and have the name more reflect the nature of the effect.
Something like "Athletic Reflexes" ect
I considered it, but it also slows down the game, makes it dependent on a highly unreliable mechanic (and that's assuming the character or their allies even invested in and use RK), and unduly punishes the player using it when they guess wrong.
This way is faster, simpler, and always works well.
There is also the factor of balance to consider. On average this is an untyped bonus of +3.75 from a single feat, which is unusual even for a feat that sometimes provides no benefit. Given that, the punishment for being wrong might not be undue.
To illustrate here is a quick count of how many enemies grant how much bonus from the feat:
no bonus: against 2% of enemies in the bestiary, this grants no bonus
+1 bonus: 11%
+2 bonus: 16%
+3 bonus: 24%
+4 bonus: 15%
+5 or higher: against 31% of enemies in the bestiary, this grants +5 or higher to your check. The max is a complete outlier at +16, most are in the 5-7 range.
Ultimately though it's what works at your table that matters. If your table is okay with the feat being strong then the feat is fine.
My only suggestion would be to lower the level to 6, and have the name more reflect the nature of the effect.
Something like "Athletic Reflexes" ect
Thanks. I will give the name some thought.
I do want it to be strong, but not "obvious must have" strong.
Maybe I will add some additional prerequisites and raise the level to where it's effect is competitive with similar powerful effects.