How are stalkers supposed to deal with indoor large fights?

makes use of emp grenades and get yourself a midrangeweapon (autoscoutrifle f.e.)

Questions like these baffel me.

Let's just get this straight. In a situation where a Heavy, sporting the health and resistances of a MAX alongside his normal health and overshield, would have trouble killing more than 1 guy if he ran inside. You are trying to enter the room unnoticed despite everyone looking at the doorways, then sit inside and you think that you should somehow be capable of murdering more than one guy while you are outnumbered 15 to 1?

The problem isn't with the Stalker, the problem is with your expectations. You don't expect an Engineer to run inside, dump an AI MANA, hop on, start shooting and earn kills. That's ridiculous! And that's kind of what you are asking for. An impossible situation where you have no right to be effective if you try to lone-wolf it.
Use classes and their repetoir for the right job. Stalkers have their uses infiltrating and murdering flankers or surprise-attacking some enemies on-route, which for instance the Heavy has much more trouble with. And vice-versa you shouldn't expect to be capable of breaching a heavily guarded room as a Stalker and then go on a killingspree.

As always, never go into a fair fight. Never. So take your time and run around. Sit in corners, during heavy fighting nobody has the time to check. Help shooting the same guys from another angle, kill enemies gone astray and generally sit and watch how the fighting is going.

First off, your a cloak which means that most of the time you choose your fights. And always keep your recon down, can't tell you how many people never use it. After these analyze your attack strategies, say like the common spider style with the old 1-2 combo. That should get you into a positive KD anyway.

Hello,

yesterday I was defending a base with a +96 people battle ( both sides, NC vs TR ) when it exploded into blood, death and pain ( lol ).

My main class is Infiltrator - Sniper, but since I couldn't do much because the base was all subterranean, I decided to go Stalker.

Died 12 times in a row xD because of the spam of granades, support fire...

So I'm really noob on this role but I would say.. never go Stalker if they are just farming you by launching grenades randomly. The best you can do is to spot enemies with your motion tools, throw some PEM, and if you are able to get their back... focus on the enemies that are far away of the middle of the battle ( engineer with turrets, sniper, medics healing 24/7... ).

you have the right idea, indoor fights using emp's can make huge impacts, its great for clearing the spam and can create pushes for your allies. Either go cqc with smg which can be very effective indoors, with the exception of cluttered areas, stay away from those, that's what heavies are for, its their main role, you can be effective everywhere else. Like someone stated darts, motion detectors are vital. Using any BA or medium ranged weapon can be very effective as well at choke points as long as you can maintain distance and cover. Get enough practice you can use your sniper rifles at close range and be as effective as most average heavy users.