I'm using charplanner; it's indicating I should get at least 3500 def (or around that).

When I check out the function for defense rating, it's a continuous curve. So can someone explain to me how this soft cap is determined? 3500 seems pretty arbitrary.

My first impression is to find the point on that curve where angle of the tangent = 45 degrees (or slope = 1, whatever you prefer).

my guess is they looked at the amount of defense you get in lethal b mods and called it that.

you could find the point where a point is worth less than half of the original slope (dy/dx|x=0=2*dy/dx|x=P) (i got 3259 in maple (eval(diff(d(dr), dr), dr = 0) = eval(2*(diff(d(dr), dr)), dr = P) for d(dr):=30* ( 1 - ( 1 - ( 1 / 30) )^( (dr/75 ) / 2.125) ) )

imo, the correct analysis would be minimizing damage taken by performing an optimization problem (I use excel GRG non-linear and evolutionary, but i used to use lagrange multipliers, others iterate over gear, or use monte-carlo schemes)

i have a whole thread about tank gearing. i even made a tl/dr this time around

http://www.swtor.com/community/showthread.php?t=970879

they might be using average numbers for high melee/ranged.