I thnik you are really overlooking Venoms and Splinter Cannons as a viable tool in the DE codex. I agree with you that our infantry isnt amazing for the cost but I find my games highly fullfilling when I mix in Dark Lances and Splinter Cannons. I absolutely love my 9 Man Trueborn with 7 Shardcarbine, 2 Splinter Cannons with the Duke in a Raider. While they do suffer that 18inch range you mentioned earlier, they pack in so much anti infantry heat that can devastate any unit inside a transport your opponent just lost to your dark lances.
I feel like you wrote this entire article about me! Seriously though, competitive list are the list that can reduce the element of luck aka reduce the probability of things you do well not happening. Not perhaps increasing the chance but lowering the chance of it not happening. This is why Redundancy plays such a role in 40k at the moment.
"The vehicle damage table is a fickle mistress"
Addressing Kirby's points, I have played games with 2 Captains in the same set up and more combat prowess and they never performed like I wanted them to. Losing scoring models really hurt in that trade off. not only that but have 2 Captains did not double how effective they were.
I forgot to mention Close Combat Oriented units who can't charge up levels are a real downer.
I guess Todd the Goalie has a different playstyle than I do but list aside, I do not think my playstyle for that army is wrong at all (as proven by my personal experience with them). The accusation of cut and paste is unfortunate as the point of the army is bike all the time and unfortunately there is only 3 biker units. Turboboosting is no longer limited to move in a straight line Todd, even with cluttered you can still get that cover save if you are smart on deployment and how you move.
The problem I have with making the army more close combat oriented is that it cant go toe to toe with a lot of C&C units as it just doesn't have the cheap invuls some armies can stack on their C&C units.
Also, the army doesn't need to kill everything your opponent bring, so trading 100percent firepower for movement and the choice to choose your engagement is a plenty.
Its different philosophies at work, I play the army with the intent to play my speed at my advantage and you prefer to play it as speed being just an answer to close the gap.