No it sounds like you are training properly for someone who is not doing contest prep! Good on ya! Most would be amazed (well you obviously seem to know) how much deadlifts and chinups (not pullups) make your bi's grow. As far as I'm concerned any program should be designed around Squats, Deadlifts, Bench and overhead press. Those should all be done heavy. Everything else is assistance. After I do the main lift(s) of the day, I hit a few "bodybuilding" exercises for the muscle group and go for a pump.
SLDLs hit the whole posterior chain...same as squats and deadlifts. The key with them for me is to find the sweet spot where you're mostly using the hamstrings - which for me is not the full range of motion. Also I do them relatively light. I squat 365 for reps, but never go over 135 for my sldl's. I could go heavier, but it would be to much on my back. It's not an isolation exercise like leg curls, so like I said, your whole P-Chain is involved.
Try them out, or try some Romanian Deadlifts. Your Deadlift will go through the roof. RDL's def hit the back more then SLDLs though.
How do you set up your 3x per week training schedule? Just curious because I do 4 days a week during winter, and 3 spring, summer, and fall. I ride a road bike 3 days a week when it's nice outside so my body can't take the extra lifting. I need the cardio of the bike because I'm the opposite of you. I can pack on mass quickly, but I have to be dialed in and on-point to cut.