I assume you're running in windowed mode.
As that page probably recommends, you can change the per application properties and disable scaling for EQ, but that just means EQ is now taking full advantage of your resolution. You can then use /chatfontsize and /mqfont to adjust sizes of chat but it doesn't help with title windows. I believe kaen had a UI he posted to help with that.
Outside of that, tricking EQ into thinking it is running full screen will allow you to set resolutions that change the size of the window, but you need to play with scaling to see what works best. Programs like IsBoxer and Borderless windows can help here.
The easiest way, however, is to turn off display scaling completely (set it to 100% in display settings) and then adjust your resolution (still in display settings) to something that looks reasonable and then launch EQ. This will make it function more like a "normal" computer than a high density display and has the added advantage of using less system resources to handle scaling while you're playing. The downside is, of course, you don't get the full benefit of that high resolution display. It's also a bit tedious to switch it back and forth before and after you're done playing. But it is by far the easiest way to get exactly what you want.