May be it's abit too early to make predictions, but i've got a feeling that majority of the community, including some mods and devs, want to have big badass space marines, while Xeno being nothing more than cannon fodder which, according to some wishlist thread which dwells in "Level design" for no apparent reason, will be dying from one bolter hit.

Forgive me for my unpoliteness, but can Devs confirm that your humble OP will be able to outshoot a Tactical Marine while playing Dire Avenger in straight fight, without blending with shadows and aiming for the back of head to get at least 50% chance of winning? Will that famous 12 y.o degenerative idiot be able to CHAARGE!!! guy in power armor and chop-chop him?

im going to be playing every single race. a marine is very agile. It will probably depend mostly on skill....

It's such a generic answer that no answer at all will be better.

What's "Skill"? Aiming skill? Skill of having good internet? Situational awareness and skill of finding advantage?

Scenario is very simple: Dire Avenger and Tactical Marine notice each other in the medium range and start spraying their weapons. In TT, it's pretty simple: those who shoot first wins. Avengers don't like being hit by bolter rounds, but their astartes counterparts don't like being hit by weapons with Rending.

There is little room to maneveur, do bunny hoping or circle strafing.

Of course, that's just one example. I'm sure Ork players will want to know about Slugga Boy vs Assault Marine scenario.

slugga boyz would EASILY lose to an assault marine. besides they are an F2P class. Its going to depend on skill because there will be NO 1V1'S. therefore teamwork, aiming, situational awareness, melee skill will all play a part.

Game release 2015, this is all still in the pipeline.
Lets wait untill there is some more information released before making any speculations on specific balancing examples.
I share your question though, but i think the developers are aware of this and will offcourse do their utmost best to make it a pleasant experience for everyone. (That's offcourse including you filthy Xenoslovers. )

Many people refer to orkz as f2p faction.

There is no need for Farseer to cast Doom on developers in such case, they'd do it themselves. There are people who love Orkz. And they'll be playing them, paying for their faction as much as Space Marine player will. So, why should they lose every time due to some insignificant references?

Also, in Dawn of War 2 slugga buys are pretty murderous. You'd want to solve their issue with machine guns, not by charging into them, of course unless you're playing Chaos Lord, Force Commander, Tyrant or Warlock.

This is probably one of the more confusing posts I have read. Are you asking if it will be hard to kill a space marine? Probably. But it can be done, and if you actually use tactics and not just lobs shots at each other, you might actually win.

Gears of war style skill will be applied, to an extend, which means crouch, roll, duck, "cover system maybe?", jump and so on will be available, if you can dodge as an ork boy that close up melta you can finish of a Space marine, in essence space marines will not be stronger then ork boys they dont want that.

Until then wait and see as many things will be revealed with time, if they make the boyz and other races lower in their hp and the like and die faster then nobody will play those races now.

Maybe eldar will have perosnal shields but lower health, maybe space marines will have damage resistance armour able to negate a certain amount of damage of their hp, maybe ork has better hp regeneration so he can regenerate faster his hp so it takes a bit more shots to take one down in combat, adrenalin rush and all that, we dont know and it is to early to know.

there is no reason to give some thought out crap to orks and eldar if you can give even the standard guardian ridiculous firepower up close, and huge agility to make them hard to hit.

as for orks, a close combat specialized ork should give a tac marine whos stupid enough to let him get even that close give a serious beating. other than that, orks simply arent MADE to stand up to a tactical in most situations.

its like trying to make a pinguin fly, it doesnt make sense.

As far as I know, Sluggas will have a fair chance in melee, but worse at range. Not sure about Shootas.