[Nokturnal]

If you position your troops strategically, you can just leave them on hold fire until they are all in position with line of sight to hit the various targets then change it to open fire. Then just sit back and watch the action.
If your men are behind cover they will not die so easily, and most of them have body armor if i remember correctly?

Stealth just means take some more time and patience. Precision is key to victory when you are greatly out numbered.
If you want to use grenades just do so from behind cover - If you use direct control mode you can see how far you can throw it and judge how far you'll need to move to be able to flush them out of the trenches.