Its my understanding that when they mean horizontal progression they mean low level players can specialize their points to equal higher level players. It means that instead of going down a very long and complicated skill tree (such as diablo 1-3) most of the skills in Eternal Crusade will be buyable from a very early stage but spread across a wider selection. Veteran players will have more options for more classes where low level players will have to pick and choose until they can catch up in levels.

Wargear is rumored to be the same way. Most of the basic options will be available to every single player, but the skill tree may add more loadout points to specific classes or unlock different or slightly advanced wargear.

Aside from Elite and Hero classes im sure the progression tree and wargear options wont be too over the top, but I'll bet there will be more armor or health options that will make even the basic classes last x1.5 times longer than they do now. Thats a pretty big increase in TTK, especially if they rework grenade/plasma/melee damage.

I know that with the dev team all they talk about is asymmetrical balance. So I dont think theyre planning on making everyone equal. There will be times where youll be taking a lv1 tactical marine and suddenly another player using a hero unit will stand right in front of you and you wont have a chance in hell 1vs1. They'll just stand there laughing as you unload 2+ clips of bolts into them and then slice you once and you die.

So. Are people just choosing to forget that things like the Mark of Nurgle will eventually be an option for all classes when they ask for a blanket increase in TTK?

Increased survivability will be an option.

Yup as long as points cost is equal to value itll be fine. Sure you may have the bonus health from mark of nurgle but youll have almost nothing else. Same goes for the stormshield, etc.

I think the real issue with marks is if point cost will change based on class. MoN traitors could become the new go-to for capping. As in, boltgun toting traitors. Throw as many mods and accessories as you can and grab some MoN sorc buddies. I would be tough to uproot that depending on where it's happening

That wouldn't be horizontal progression. That'd be vertical progression.
A lvl1 character on wow cant beat a lvl 90, they can reach that lvl and be equal to them, that doesn't make it horizontal.
Horizontal is when players progress they wont get 'stronger' than a new player, they'll just have better options.
Also this is a shooter, with shooter style progression, not an MMO, MMO things wouldn't work for this game, as we can see from The Division and similar games.

I'm assuming wargear means weapon attachments and perks, similar to any generic shooter, which would be a good thing because anything else just wouldn't work for the game.

See, a player at rank X having their hp increased x1.5 where a new player wouldn't have that... would not be balanced.

Asymmetrical balance is about classes and factions, not individual players, that'd break the game completely.

1shoting with a basic attack with generic sword as a hero would be pretty silly, hence why I say increase TTK, make fights last a bit longer and be more fun.
Also since TTK currently allows you to be 2 hit by an axe, its not giving much room for different weapon types/classes.

That could totally be true, but a possible counter could be specialized rounds to do more health or armor damage for additional loadout points. Or possibly the mark of nurgle slows the movement speed of the traitor meaning there is a disadvantage to its tankyness. Either way the MoN is already a very powerful point capturer. I'm kinda excited about the idea of slow moving traitor marines with boltguns and nothing else.

Ammo Types and thoughts:
Hellfire could do more damage vs Health which would specifically hurt Marks of Nurgle who have no armor bar. It would also be effective vs lightly armored classes or tyranids.

Kraken bolts could do more damage to the armor bar and more damage to heavily armored units such as terminators or heros.

Inferno rounds could do apply a burn effect that stacks with melta or flamers burn damage. Useful against high health targets you have to continuously do damage to otherwise theyll regenerate or recover.

Source page for ammo types: http://warhammer40k.wikia.com/wiki/Bolter_Ammunition

I think you misunderstand. The options are available to a lv 1 as much as they are available to a level 5. The difference is amount of points they can spend buying those traits.

Lets say Im a lv 1 Eldar player and i have 1000 loadout points. He can still equip any of the wargear a lv 5 can. He can spec his beginning progression points into a health boost and bonuses for his classes getting that x1.5 health. Same options.

However the lv 5 has more of those spec points to spend, one of those spec points may increase not only his health but increase his loadout points to 1250 instead of 1000. Once again, same options as that lv 1.

That lv 1 player can still spend his in game points to spawn as a elite or hero, being just as strong as a veterans elite or hero. Its not an unfair advantage, its horizontal progression. It means that you dont have to climb down a tree of level ups in order to get on everyone elses level. You can specialize and be just as strong at level 1-2 as a level 5. That level 5 however doesnt have to be as greedy with his points and can branch out a little more.

However you look at it Elite and Hero classes will have to be stronger than the basic classes. More Health, more wargear, better equipment. Somehow these units gotta stand apart from the rest. Its not a game breaking mechanic either. Star wars battlefront II used this "not everyone is equal" system really well. The big thing is balancing the classes with requisition costs and limitations.

Just a short question, where are you playing from? If you play from somewhere else then the North American Continent please stop to complain. We had a lot of discutions about the ping.