So first of all input lag is not the regular lag you get in game that shows in the bottom right corner:
This is just the normal latency in game it will vary depending on your distance with the server, but this will help us get the correct settings to fix your input lag so now lets follow some steps to do that:
STEP 1 - CHECK INITIAL VALUE
Type the following in game and press enter:
/dump GetCVar("SpellQueueWindow")
If done correctly you should see a number like this:
That number is your SpellQueueWindow if you never done this before it should be 400 thats the default value, The SpellQueueWindow is the amount of time you have to press to prepare a spell before your global cooldown ends that way as soon as it does your next spell will go off, the problem is when this is too high or too low, if its too high your keys will feel slow and sticky but if too low youll have to button mash to get spells to go off.
STEP 2 - CHANGE VALUE
The value you want there will depend on your world ms latency that we saw at the start, in my case it was 157 so you want to add a number between 80 to 150 to that, you do have to do a bit of testing to figure out what feels best for you in my case I started adding 150 and then lowered my way down to 83 just to get a nice round number at 240
To change the value you have to do the following command, for this example we will add 143 to my base latency of 157 that will give us the value of 300
/console SpellQueueWindow 300
You press enter and now the value has changed although no confirmation message will apear.
STEP 3 - CHECK IF IT CHANGED
So to check if it changed we have to use this command again:
/dump GetCVar("SpellQueueWindow")
And thats it you have successfully changed your input lag test out different values and see witch one feels better.
I hope this guide helped you can find more content here:
