Translating into numbers:
5+30*(1-(1-(0,01/0,3))^((2000/50)/2,5))+30*(1-(1-(0,01/0,3))^((300/50)/0,45))
which equals
5+30*(1-0,58)+30*(1-0,64)
which equals
5+30*0,42+30*0,36
which equals
5+12,6+10,8
which equals
28,4
This is only a rough calcualtion, the actual value with 2000 wp & 300 crit is 28,47. Don't forget the skill/talent buff as well which may increase crit up to 11%. BTW copy & paste the 1st line into excel or the equivalent to get the exact result and/or toy around with different numbers for wp & crit rating to get the desired result/threshold.