For me, until recently, I always had weak lats. I couldn't do 1 pull up, and my V taper was more like a U taper. I did endless lat pulls, but I couldn't hit my lats hard enough with them. About six months ago, I started focusing on back width, mainly using the hammer lat machine and doing some assisted pull ups.
On the hammer lat machine I started with just a 35 pound plate on each side, and in six months I progressed to 2 45s and a 25 on each side. I could feel the burn in my lats for the first time ever....it was like I discovered a new muscle group in my body. Now I can also do 5 pull ups in a row without assistance and theres also a defined V taper that was never there before.
Maybe you just need to try different exercises until you find one that will hit YOUR muscles the best. Also I think that heavy compound back exercises such as pull ups and bent over rows spur growth in biceps. Biceps were designed mainly to assist with the back movements, not do isolated curls. I think your biceps will grow once your back starts growing again.
You don't deadlifts.....why even lift weights
? I live to deadlift. My all time favorite exercise. Give em a chance man, you might like em.
My back day:
-Deadlifts
-Pull Ups
-Bent Over Rows
-Hammer Lat Pulls
-Weighted Hyperextensions
Good luck man.