Actix provides actor abstraction over synchronous code and allows to communicate with it in async manner. TechEmpower benchmarks uses sync actors for db operations and http part is async. I am not sure how this help though, tokio-minihttp also uses threadpool for db operations, results are not that good
i think from ergonomics standpoint, actix is very close to rocket. of course rocket has some advantage, but actix compiles on stable and has zero codegen code. as soon as proc macro stabilizes both will be on par.
from performance perspective, actix is faster than rocket on any type of load.
first, you need to define what is crash in rust means. panic or error. in general case you can not recover from panic. in case of error, type system prevents unhanded errors in actors. you can restart actor, but that is controlled by developer action.
a lot of has changed since 2015. scalable http/1, http2/, websockets libraries and frameworks are available. and with async/await async programming will be even simpler.
Writing good docs is hard for sure! Especially for developers, you just want to write cool code :) but take into an account lifetime of the projects, compared to python all of them pretty young. For example I started actix-web just 5 months ago, sure it needs more documentation