One thing I think that is missing from the current 5th edition codices is army flavour.
Remember how you used to take doctrines or traits to play your force. Now it is only characters.
Well, so yes there is some flavour, but the idea of having to buy a character to have that level of flavour is absurd.
In my mind there are 3 codices with the biggest problems in the field of flavour.
-Space Marines
-Imperial Guard
-Chaos Space Marines
First off Space Marines. This is the codex of characters. To play Crimson Fists you need Kantor, Salamanders require Vulkan. Okay so GW says "Well that doesn't have to actually be Kantor, you can say he "counts as" someone else." NO! Why should all my crimson fists captains have a sweet storm bolter and power fist. Do they get promoted and the chapter master issue them a copy of his gear. NO! And in the case of the salamanders, you are talking about a character armed with 3 of the Primarch's own weapons. WHY WOULD ANYONE ELSE HAVE THEM?!?!
I should be able to play the chapter I want with the feel it should have without taking a specific person.
THE SOLUTION: When I buy a generic Captain, he should come with combat tactics for free and then for X number of points, I can buy one of the other chapter tactics. This way, I can have an Imperial Fist army without a Terminator Lord, or a crimson fist captain with a power weapon and actually have them feel like an Imperial Fist or a Crimson Fist.
Okay, Imperial Guard.
Well the problem they have is characters again. I think even more so than the Space Marines. At least in the SM codex, you have to choose between which chapter tactic you take. In the Imperial Guard Codex, you can buy in one list if you desire 10 characters (Creed, Kell, Dedd-dog, 1 other HQ, Pask, Harker, Bastonne, Chenkov, Al-Rahem, Marbo). All from different regiments. And you can get all their benefits.
Some should be combinable, such as Bastonne and Creed or Straken and Harker. And Marbo should only ever be catachan!
And Valkyries: do you know how few regiments actually have these things. Not many. But heck, why not let everyone take them.
I don't know a solution here. They took away flavour by removing doctrines and replaced it with a congeal it all approach.
Finally, CSM. I'd rather call it codex Death Guard. Chaos, which is supposed to be one of the most flavourful codices I'd say is one of the dryest. Marking units does little. The MoK is more like the Mark of Terminator Honours. +1 A does not make you khorne I'd say. Furious Charge does. This is particular bad in the HQ section where you can have a Khorne Lord who doesn't feel like Khorne.
Furthermore, the only good way to play CSM is all mech. And on top of that, Plague Marine mech. Why take anything else when you can take plague marines.
I'll be the first to say that CSM is a virtually perfect balanced codex. The only thing is, GW did this at the expense of the one thing that defines an army: Flavour.
You can't play several of the legions at all really. And anything but Deathguard is just not the best way to play it. Heck, my friend is going to be using Blood Angels for his world eaters once the codex comes out, just so he can actually get furious charge.
SOLUTION: There are 2 here. Codex Legions to give me the rest of the options of chaos. Iron Warriors, Night Lords etc. etc.
The other is to improve the marks to make troops other than cult troopers feel like they are devoted to their god.