I bought an N52 years ago and it just totally sucks IMO. I've never even been able to give it away. Maybe if you have some tiny little hand that actually can use the wrist rest, then it could be good, but I have to cramp myself to use it and it doesn't provide any more buttons than the left half of the keyboard does. I tried it recently for AOC, but it still sucks. The D-pad was my idea for swings too, but it's just not coordinated enough when you add shields in and having to do combos. Plus, how your thumb rests on it about 90 degrees off from normal is just weird.
The smart way to game on an MMO is with the keyboard and a quality mouse that has some thumb buttons that you can bind to CTRL, ALT, or Shift. I have my 2 bound to CTRL and ALT thru the Razer software. This way you can bind CTRL-1 or ALT-2 or whatever to a whole other action bar. Binding one function to mouse buttons is pretty dumb IMO, when you can open up a ton more options using a modifier key.
Make your setup so that similar skills are used between the same key, but different through the CTRL or ALT modifiers. For example, I have Q-E-R setup as my upper attacks, CTRL-Q-E-R is reserved for the lower attacks, and ALT-Q-E-R are for my shields. 1 & 2 are left combos, 3 & 4 are center combos, 5 & 6 are right combos.
As for the reserved key errors, you get them because you haven't cleared the old binding. Just make sure to click 'Apply' after every one you change and you shouldn't get the errors.
There is also a fix for that mod. It takes about 5 minutes to do it.
Here's how my UI looks with MirageUI and binding the keys as I said. A+ is Alt plus key, C+ is Ctrl plus key.