Importantly: 4e NPCs should almost always be modelled as
monsters, not as player characters, even if they superficially resemble PCs. This is a huge departure from previous editions. There's a difference between what's
fun to use (player powers) and what is fun to have used
on you (monster powers). The two follow different rule sets and enjoy different freedoms, and that's pretty important. The system is based on it. For instance: PCs can pretty easily one-hit-kill other PCs if they try; they're really not designed to battle each other. —
Jonathan Hobbs 57 mins ago