You will be moving around much more in this game than others, so I would say it would affect your use of hotkeys a bit. You could always keybind the keys around the arrows as hotkeys.
Nostromo N52 pad and Mouse here. Only use the keyboard for chat. 8)
..to move and my Mouse in the Right hand for Camera control.
How will that affect me using hotkeys?
I despise WASD.
It all depends on how comfortable you are with your key selection, and what type of keyboard layout you have.
If I were to use the Arrow Keys to move, I would have 8 hotkeys (not including Enter - which you typically can't rebind) at my fingertips. If I were accustomed to using Arrow Keys, I could have upwards to 13, which would give you considerable flexibility - but not to the same level as someone using the 'standard' WASD.
Luckily for you, TERA has a 'chain' system, where you can set cascading skill chains to be activated with a hotkey (Default is Spacebar). So, if I use one ability, I can set it to use a second ability when I hit Spacebar (if the situation is appropriate for the second ability), which can then chain into another ability, and another, and another. While not optimum, it does alleviate some of the hotkey constraints you may face - depending on your playstyle.
I would not suggest being aggressive with your playstyle, or focusing too much on PvP, if you're relying on the Chain system over hotkeys due to the reduced flexibility.
/used to FPS as an Arrow Key
//Swapped to WASD for flexibility
///never looked back
Mouse is automatically set up as camera, and your first 2 abilities are attached to your mouse buttons, so if you just use those two abilities you're set. :)
However, I do see it being a problem using a standard keyboard just because the other keys are out of reach. Probably better off using the numlock section for your hotkeys, think it'd be much easier to adjust to.
However, I do think that the wasd keys do allow for an easier reach of hotkeys since they're by more keys than the arrow keys. I find myself using 1-5 for my main abilities as well as my 2 mouse buttons. I also partake in using my ps3 controller for relaxation and ease of use. Actuall find it much easier to hit my hotkeys and move. Also aiming doesn't seem that different than when using my mouse.
Use a Gamepad (Xbox 360 controller) or re-key your bindings to something more comfortable. I generally play ESDF over WASD. But, the gamepad will definitely be a wrist relief for casual playing. :)
..to move and my Mouse in the Right hand for Camera control.
How will that affect me using hotkeys?
I despise WASD.
Uhm.
Look, you aim and attack with your mouse. LMB/RMB are two of your skills right there, and then you aim by moving your mouse around. You're going to want to use WASD. I honestly never used WASD until I started playing TERA, and I would be [filtered] without it.
Suggestions -
A.) get used to WASD and get a Naga for your skills
B.) get a gamepad or controller
C.) don't play TERA :/
You are NOT going to be able to play the game properly/well if you use your arrow keys to move, period. The game is just not designed in such a way where you can do that. WASD & Space & F & your mouse are your main tools in TERA, and you need masterful use of them if you're not going to die. BAMs and Bosses will [filtered] you up, and you'll miss a lot, unless you have a proper setup for TERA.