Having supported (from an infra/ops point of view) several places that insisted on using Wordpress, I don't understand why Varnish in front of isn't the standard 'recommended' way of hosting it. 1: it isn't going to matter. When the WP PHP is doing 30 different SQL queries just to load the front page of the site, your web server is no longer the bottleneck, even if it's Pre-Fork Apache with mod_php.
Using Varnishis a huge boost in performance for sure, but it doesn't solve vulnerability and maintenance problems
For those who aren't able/willing to use a fully static version of the site, Varnish (or Apache Traffic Server, Squid, or Apache or Nginx's Cache mode) can provide a huge improvement in performance, and (definitely with Varnish and a custom VCL, possibly not as easy with others) can even handle stuff like grace mode (i.e. return cached, expired results if the origin is offline) and purging cached objects when they're updated in the WP DB (via a plugin which communicates with Varnish).
Im not sure what you mean about maintenance problems?