If you have 10 HP or less then you will die from single shot of Runner’s SMG. That’s how games work.
Well, if you use Soft Point ammo against armor or miss most of your shots then yes, it is going to take that much of bullets to drop a hunter on Skirmish.
However, you always have an option to change in-game difficulty to Adventurer for machines having less HP. Also, using Armor Piercing ammo and landing most of your shots also helps.
For comparison, it took me 1090 rounds of 7.62mm AP ammo and 331 rounds of 9mm FMJ SMG ammo to kill one level 4 rival FNIX tank, where 98% of the bullets hit and that on Guerilla difficulty, in solo game, without any help from others. (I know the exact ammo count since i have that gameplay recorded.)
Oh, in MP game, set the “Auto Scaling” to OFF if you don’t want loads of machines. Since when it is turned ON, the more people are in your game - the more machines there will be.
Sounds like Paskallaholm safehouse (Forest region). In that safehouse, you spawn in 2nd floor and there is no way hunters can kill you right after you spawned.
Even when the house is surrounded by hunters and you can’t make a clean exit (have happened to me few times at that loc), you do have an option to spawn in a different safehouse. Why not use it?