Yo Doc,
I like to have variety with my cardio to avoid burnout, and right now I am doing thee things.
-Incline waking at 3 mph with a 10% incline for 30 mins once a week
-Concept2 rower at resistance of three, shooting for 6,000 m (usually get around 6,400) in 30 minutes once a week
-Jump rope, 15 rounds of 90 seconds on 30 seconds off for 30 minutes, twice a week.
For all these, my speed or intensity is pretty much the same the whole workout, but my heart rate isn’t. For walking it’s 110 -130 bpm the whole workout. For rowing it doesn’t get over 110 until about 15 minutes, and peaks at like 125 at the end. And for jump rope, it’s around 90 BPM the first 15 minutes, and at the end I am hitting 130 - 140.
I feel like I should be at 110-120 for LISS the whole workout, not just the tail end? Is this normal, is it not a big deal, and am I overthinking this?
I am less concerned with the heart rate as compared to the volume. Looks like about 90 minutes of conditioning per week, which is about half of what I’d like to see outside of a barbell sport athlete prepping for a meet
I’d favor doubling up on the walking and rowing, along with changing the damper to probably 4-5 on the resistance setting to get the drag right).
I can certainly increase the damper. I used to run it higher.
Regarding 90 minutes a week, 30 minutes of treadmill, 30 minutes of rowing, and then two 30 minute sessions of jump rope a week? I get that I am resting a 25% of the time on the jump rope, but surely that counts for more than 30 minutes for two sessions a week?
I feel your comment to my core. But, the amount of cardio that is required is a lot of cardio. And, that’s the minimum. 
Understanding this and applying it got me to realize how important movement is. But, applying it also got me feeling much better too.
On top of meeting the minimum, I also strength training and run. It’s a lot. But, eventually you start to enjoy it. You just have to get into a routine with it all.
Regarding 90 minutes a week, 30 minutes of treadmill, 30 minutes of rowing, and then two 30 minute sessions of jump rope a week? I get that I am resting a 25% of the time on the jump rope, but surely that counts for more than 30 minutes for two sessions a week?
Ah, sorry. I must’ve been reading too fast. Still, the point remains that I would want most people to be doing more than 120-minutes of conditioning per week. You’re likely getting 120 to 150 MET-min of each from bout of conditioning. That’s about 480 to 600 MET-min/wk. I think most people would benefit from more conditioning. I don’t have any issues with the high intensity interval training (HIIT), though I do have concerns about the cost of that related to your RT goals. If it were me, I’d recommend doubling the rowing and walking.