If real life weapon technology is 10, than armour technology is at best a 5, with infantry armour at best a 2. 40k gets around this by having a better damage/armour balance in terms of technology, and a lot of races that do use melee are physically suited for it. Space marines are supposed to be able to shrug off most small arms fire and get stuck in melee, where their speed and strength counts so much. Eldar are just as fast as marines and sneaky too, while Orks are strong but can soak up casaulities like a shroom sponge. IG and Tau don't do melee exactly because they have a "real life like" situation, where they are weak but have nice ranged shooting. Also, friendly fire should be turned off and Space Marine had a great melee system that did not suffer from these "limitations" . Skyrim's melee worked too. This is the worst melee system in the history of gaming, clunky, overcomplicated and handicapped.
I hoped for a melee system like that of war of the roses, with parrying blows, aiming at weak points, free movement while swinging and so on... I still dream of it... :/
Ranged - Aim, fire, control recoil, aim for the head, ADAD spam (optional), keep track of ADAD spamming target. Melee - Cluster fuck of luck and gambling. The system does not reward skill, it encourages guesswork.
Agree with most of what you said except Eldar are generally faster then marines both in movement speed and reaction time. This is represented in the TT by a higher iniative stat(atleast until 8th edition). It is not fairly represented in EC IMO.
In most lore books, they are supported to be around the same superhuman speed. Remember that unlike TT, marines are usually outnumbered at least 10 to 1 in most books. If we go for TT, the old version had a lot of stupid, like combi and twinlink, the new version have the weird AOE hit stuff that doesn't make sense, instead of blast templates.
The only thing that needs to go in th ranged equation is the ADAD spam. That should really mess up your aim, like decrease your accuracy by half!
Well than we need an even bigger aiming detriment because I still see peopel dancing around - it looks retarded but it works when it shouldn't.