It’s not an issue of being an EE fanboy. I like EE but I’ve put up far more sites on other platforms. EE is a sweet value for custom work.
I’ve been building and managing internet sites since 1995 on every platform imaginable. I designed and managed an e-commerce site with a few million registered users and over $200-million in annual revenue. The booking application was written in Tcl (tickle), which is far less capable or powerful than PHP is now. How could it handle the heavy traffic needed? Plenty of load balanced web servers, plenty of application servers, and a few giant, dedicated databases (not to mention a few dozen people to keep it all running).
Again, a site with tens of thousands of articles will not be a big deal on EE. The hardware will be the issue. A simple site like MacDailyNews probably has tens of thousands of articles but requires a lot more horsepower than a simple blog site. EE probably has other sites which are far larger, have more content, more complexity already than what you’ve outlined.
Drop a note to EE sales asking for a list, and drop one to Nevin at EngineHosting for additional detail. I don’t think you’ll be disappointed in EE’s capabilities.
As to creating a site that is “news” oriented, say, like CNN.com or USAToday.com, where the amount of content becomes enormous, and bells and whistles complex, there are far more organizational issues to contend with than whether PHP/MySQL can handle it, or whether EE can meet the requirements (whatever they might be; after all, EE is a “value” CMS and doesn’t come with all the bells and whistles of huge and complex sites like CNN.com or USAToday.com, but could compete quite well with the proper PHP resources).
In situations like this, it’s always best to outline in as much detail as possible all the requirements you can come up with, then match that to the resources you have available for the project, then match both to the various CMS tools available; trying out those that hold the most promise. EE might be overkill. It might not be sufficient. But know what you want to accomplish with some semblance of detail before making a commitment.