balance+3rd jobs+high rate = error
What type of high rate are you talking about? High in rates or high in rates AND lvs?
If you are talking about high lvs like base lv 200+ you will get people abusing the skills with no fixed cast times since the skills with only variable cast time can get 0 cast time.
If you are talking about just high in rates like a 150/50 for 3rd classes with 10k/10k/2 in rates then your worse nightmare is Gate of Hellalmost every single stuff from Shura, Dragon's Breath/Some Rune stuff from Rune Knight and Hell's Plant/Cart Canoon from Genetic mostly if some fixs/updates aren't applied. Shura have like spam non-stop from lots of stuff along with the "mini ranged asura" Gate of Hell, Rune Knight have Dragon's Breath ignoring almost all reduces except pasana/fire armor and some minor stuff, Genetic can spam Cart Canoon insta with food and god items and make people not being able to move thx to hit lock and the same works with hell plants[or whatever hell plants does that is annoying as crap].
This is what comes from memory, some stuff can be wrong tho. Note that this is if there isn't some updates applied.