[_asummers]

I've noticed higher CP pokemon tend to run away more quickly. You also have to remember that there's now great balls and razz berries to influence throw chances, so the client probably publishes the events it's doing (gave a razz berry, threw a pokeball, threw a greatball) and the server creates some randomness that says yes/no.

[uryga]

That "randomness generating" still seems like it would be easily done locally, and it'd reduce server load. But maybe there's some more advanced mechanisms we don't know of.

[corobo]

if it's done locally then people will bodge the client so the random is no longer random. The server's always going to have to do the math, even if to just ensure the client's not lying.