This makes no sense, my lvl100 engineer uses 9 skills (and i love them all). Maybe your just not very good
"You need 5x NV to get the key to drop even so don't worry, to reach the input limit I think you have to create a game per minute for more than 2 hours or something like that. "
Ahh, i thought it was like 7 games an hour, thanks for correction. I can get 5 stacks in under 5mins if i dont have to look around to much. I can see people doing festering woods to get 4stacks, pick up an elite somewhere else for the 5th then hitting the keyboss. A2 you can use desolate sands (lots of elites, if not go into voa). Act3 we can just do the bridge, always at least 4 there, can hit the cave to get the 5th.
The problem im seeing is the a4 key, there are barely any elites there as it is, its going to take forever to get the 5 stacks. Are keys tradeable (rmah)? I know the ring isnt.
D3 devs should bite the bullet and do some sort of map system, its really really fun and keeps things fresh with new dungeon layouts and monster combo's.