Can't seem to reduce speed through Dulles (and WPT in general) via moving mountains

We have a Wordpress site that caches via WP Rocket, Cloudflare, and most recently today MaxCDN/StackPath. It’s at:

Over the last week we upgraded our aging dedicated server to a newer dedicated server so we could utilize PHP 7 (previously was on 5.6) and make use of Memcached, Mod_Ruid2, and Opcode Caching (OpCache). That’s all done.

We’ve optimized everything we can think or research about, and our speeds are now either competitive or way better than our closest competitor in our field, which is

Yet in WPT, especially in Dulles, VA (the default test spot) - they stay a cool, consistent 2.2 - 2.6s First View, while we struggle to get even close to 3.3s (which is our best).

However, in other test areas (MaxCDN/StackPath rep called our speed tests ‘the bomb’ and showed us 5 different ISPs in the Philadelphia area with fully loaded times of 700ms, no browser cache), and through our own personal testing, we’re getting amazing speeds.

Less than 1 second in most places, and less than 2 seconds everywhere else. Except WPT. Even though we have straight A’s across the board, and our competitor has no static content cache, doesn’t use SSL for anything, etc.

Can anyone help us to understand why we can’t get better First View times in WPT, while the improvements we’ve made have made us much faster virtually everywhere else? What are we missing?

My boss really wants to rely on WPT as the main metric, and really wants to be faster than our competitor in every possible way, so I’m just trying to accommodate that.

Thanks for any help and insights you guys can provide, I really appreciate it!