You wont have many issues unless it dips repeatedly and too fast from to below 30-40 all the time.
I play on those monitors for 3 years now, the 27' version and in WoW cause WoW is a shit game in that matter, it goes to below 40 FPS all the time, never notice anything different mostly because WoW doesnt go up and down a lot, its simply low
The monitors have many more things than just "144Hz" as to why they are better than a default 60Hz.
Also that monitor is the old model, the newer one literally released last week , its the same exact thing just with a newer panel basically and costs the same averagely, obviously thats why the old model is on sale :P
The new models are G2590PX and G2790PX.
If you are planning to change GPU when they release, go with a 144Hz screen, WoW or not.