You are waaaay overestimating the gods. The only Asgardians with any real power are Thor, Loki, and Odin. I give the warriors three, Baldar, Sif and whatsisname there on the bridge a little better than average Asgardian ability... but the rest of them are no tougher than Luke Cage. You assume they can just kill the humans if they wanted to, but it's nowhere near that easy. Norman has launched a serious threat on Asgard, and many of it's residents are in danger of their lives.
Heimdall is the dude who guards the bridge.