The JPG you uploaded is fairly over-compressed but looking closer, I was able to see.
This looks average for IPS 1440p for a third-party implementation not made by a big organization (non-NVIDIA, non-Samsung). Top/bottom extreme crosstalk is quite normal.
How many percent did you increase VT? Did you try lowering refresh rate first?
Generally, you need to increase VT by 25%-50% to see human-noticeable difference in crosstalk, and usually the only way to increase VT by such big margins is to do it during lower refresh rates (e.g. 100Hz). Large VT's massively increase the bandwidth requirements of the video cable when we're trying to use large blanking intervals GPU-side (BenQ/ZOWIE/LG technique) instead of monitor-motherboard-side (NVIDIA/ULMB technique). Mathematically, large VT's needs to be multiple milliseconds long. For example, a Vertical Total of 1900 at 1440p means 1440/1900ths of a refresh cycle is spent refreshing and (1900-1440)/1900ths of a refresh cycle is spent in VBI between refresh cycles. But VT1900 is impossible at 144Hz, and requires dramatic lowering of Hz to work. VT1500 and VT1600 will not be worthwhile investments in trying to reduce strobe crosstalk, you must try to VT 50% bigger to see big improvement, and 25% bigger to see slight improvement.
The "bigger-crosstalk-free-zone" effect is successfully observed on BenQ/ZOWIE (especially at 144Hz) and was observed to an extent on LG 240Hz.
There is no guarantee large VT tricks work on ASUS monitors but try (A) testing 100Hz strobed default, then (B) switch back to 144Hz and then derive a large-VT 100Hz strobed using the Appendix A instructions of
http://www.blurbusters.com/crosstalk#appendixa to modify a 144Hz small-VT mode into a 100Hz large-VT mode while keeping pixel clock (Dot Clock) unchanged... You may get the crosstalk-free-zone-widening effect roughly similar to the above if your monitor scanout velocity stays at its full max-Hz velocity during the lower-Hz operation.
Also, in addition to the above, you can also help reduce crosstalk by narrowing dynamic range a smidgen (5% or so) -- increasing digital black levels and reducing digital white levels (e.g. via NVIDIA Control Panel) since the fulldark / fullbright colors are the ones that generate the most problematic ghosting and maximum strobe crosstalk. (That's why LightBoost had crappy colors... it intentionally reduced dynamic range). Many of us prefer the colorful full dynamic range, but we do have the option to intentionally reduce the dynamic range via various adjustments to try to reduce ghosting/crosstalk further.