Hello Finnish fellow! I guess the problem is within a few attacks, according to my CoH / CoV Character Builder there are a few attacks with unnaturally high endurance cost for being early moves.
End--Rchg
9----8 Slug
10---8 Buckshot
15--16 M30 Grenade
10--20 Beanbag
14--12 Sniper Rifle
22--20 Flamethrower
Go figure! 
And note that their base accuracy isn't that good. My character builder says it is 5% for most of the things. For most radiation blasts the base accuracy is 10%!
I think it is just you using attacks very much, that drains endurance worse than a Mu Guardian!
wow, there is something wrong there, fire/thermal is a very endurance heavy power pool and uu were running out before him!?
AR is now a very poor choice of power pool unfortunately (in my opinion). My only lvl 50 is an AR/Dev blaster who was hit so hard by ED that she's really no fun to play any more.
There are too many compromises and with AR they all result in a reduction of a key aspect of the AT that wrecks it. You either have very little accuracy, very little damage or very little endurance or you split your slots for two enhancements of each type and are then hopeless at everything.
Would I roll another AR balster? Not on your life, unless they make huge changes to give it a chance of actually being a blaster again.
Your post amazes me, is there any chance of you posting your build to see where the problem is? I find AR borderline of not needing stamina personally, very borderline but AR/(thermal,traps,kin) isnt AR/dev, looking at your build may help in finding the problem. I think traps would be the most compatible anyway due to AR action times, the rest arent so bad and some nowhere near as bad.
He will honor his words; he will definitely carry out his actions. What he promises he will fulfill. He does not care about his bodily self, putting his life and death aside to come forward for another's troubled besiegement. He does not boast about his ability, or shamelessly extol his own virtues. - Sima Qian.
I don't find AR bad, it has some good lethal attacks, 2 fire attacks, stun and full auto (combined with fulcrum shift and siphon speed) has pretty good recharge rate.
But the levels under 20 I always find pain to level due the end drain (atm every one of them has stamina).
Also it's pretty hard to use less attacks when I'm soloing, that is when I have problems (pre-stamina that is). 
As for the build, every AR corruptor I've met have the exactly same problem, they run out of breath too easy.
My build isn't really that special, only end reduction enchantment I had was on grenade launcher since it's the attack that drains me most (mostly use burst, slug, sniper rifle and grenade only if it's worth it and not a suicide), mostly damage and accuracy.
Now when I got stamina 3 slotted It's alot easier to lvl, but the levels under 20 were pain, especially fighting Mu on those arachnos maps, I sometimes ended up face to face with a Mu and waited for end to recharge so I could do a lousy burst, then I got drained by their attacks again...
i would of gone buckshot before m30 grenade, if your hitting less than 6-7 with m30 grenade it really doesnt pay for itself as much. AR is most definately not broken.
He will honor his words; he will definitely carry out his actions. What he promises he will fulfill. He does not care about his bodily self, putting his life and death aside to come forward for another's troubled besiegement. He does not boast about his ability, or shamelessly extol his own virtues. - Sima Qian.
The powers really do use ALOT of endurance, even if you don't get m30.
I've been in a team with other corruptors AR and not, I've noticed how the end bar of AR corruptors goes down faster than other corruptors.
Also I rolled an ice/kin corruptor and lvled him to lvl 15 before my AR/kin and I hardly ever ran out of end in midle of fight.
The attacks of AR use alot of end, considering it is an assault rifle and has draw time.
AR is abit out of whack possibly, I remade my AR/traps because she wasn't so hot for pvp which I found I quite liked so remade her as nrg/kin, but yeah I was out of end waaayy before any other team members.
Maybe its corrupter side then. I know the chance of toggle drop is different, my AR on coh's endurance bar only drops if i have left superjump on (and i always leave ss on) a fireblaster i know burns through endurance alot more than i do in much less time but the balance is in the damage to endurance ratio and certain secondary tool effects i gain from my set that they dont.
He will honor his words; he will definitely carry out his actions. What he promises he will fulfill. He does not care about his bodily self, putting his life and death aside to come forward for another's troubled besiegement. He does not boast about his ability, or shamelessly extol his own virtues. - Sima Qian.
I think they should lower the end cost of powers, after all, how many gun toting people you see catching breath after few shots? AR needs some end cost reduction, badly.
Otherwise it's very nice powerset, nice AOE's, good lethal/fire attacks (the full auto rechargers pretty darn fast aswell) combined with fulcrum shift and later on Ghost Widows patron powers. 
My blaster needs to catch her breath from carrying the great big gun.
Endurance costwise over the set its about average compared to other ranged primaries. Many other sets just dont get the equivalent to m30 grenade and buckshot endurance cost wise pre stamina level.
He will honor his words; he will definitely carry out his actions. What he promises he will fulfill. He does not care about his bodily self, putting his life and death aside to come forward for another's troubled besiegement. He does not boast about his ability, or shamelessly extol his own virtues. - Sima Qian.
Not my huge corruptor, besides I've seen bigger guns.
And the endurance costs of m30 and few are high for early powers (as you can see on the 2nd post), the problem is mainly pre-stamina (and a little bit after it). The pre-stamina levels are horrid to level, especially when fighting Arachnos Mu or similiar.
I think it's a problem if you can't attack properly for the first twenty levels of your toon.
[ QUOTE ]
I think it's a problem if you can't attack properly for the first twenty levels of your toon.
[/ QUOTE ]Welcome to the world of non- /regens 
Bah, my dark scrapper or ice corruptor out-soloed my pre-stamina AR corruptor any day of the week, weekend and twice on sundays.
I rolled an AR/thermal corruptor long time ago when I first got Cov and I noticed how I always ran out of endurance when I pulled few attacks, so I was reduced to do just healing.
And few months after that I decided to try AR/traps corruptor, again I'd run out of breath all the time. I even teamed with a fire/thermal corruptor for test and he could keep attacking and healing us both without having any bigger end issues (we were both lvl 17 and according to him he only had one end reduction ench). Even when I didn't use any of my traps I ran out of end.
Now, few weeks ago I rolled third AR corruptor, kinetics this time, still can't keep attacking proplerly without stamina.
Is AR really suppose to be like this? I know it has modified accuracy, but is pulling a trigger really that tough?
By the way: My corruptors are lvl 18, 21 and 24