RWD, dude, you just said you are making ****ty gains on your legs doing 11-15 sets, but you are making huge gains with 3 sets on your other body parts. You answered your own question.
Here's a few suggestions:
1) Lower the number of sets/exercises for your legs. Try to keep the number of sets between 6-8 using 1 or 2 exercises total (i.e. Squats and Stiff legged dead lifts)
(paired with)
2) Using a more moderate rep range like 6-8/8-10...or if you really like pyramid sets (10, 8, 6, 4)
3) Since you work legs twice a week, make one a high weight day while the other is a med/high rep day
or finally...
4) Use different movements between the 2 days you work legs...
-day 1- squats/stiff legged deads...etc
-day 2- front squats/split squats/lunges...etc
Here's a few suggestions:
1) Lower the number of sets/exercises for your legs. Try to keep the number of sets between 6-8 using 1 or 2 exercises total (i.e. Squats and Stiff legged dead lifts)
(paired with)
2) Using a more moderate rep range like 6-8/8-10...or if you really like pyramid sets (10, 8, 6, 4)
3) Since you work legs twice a week, make one a high weight day while the other is a med/high rep day
or finally...
4) Use different movements between the 2 days you work legs...
-day 1- squats/stiff legged deads...etc
-day 2- front squats/split squats/lunges...etc