LED driver suitability and circuit advice
To answer your questions in order:


  whether this really is a suitable driver?


Yes. It looks like it will work. 


  Also if I were to increase the number of LEDs to 12 (requiring a total
  of 36v) would the LEDs function as normal but the last one appear
  dimmer?


No. LEDs don't work like that. If you go over the maximum voltage requirement then all of the LEDs will be off.


  Lastly, I'm unsure if I should add a dropping resistor at the start of
  the circuit, and if so is the following calculation (for 10 LEDs)
  correct?


No resistor in series with the LEDs is needed. You use a resistor to drive an LED if you have a constant voltage driver. This is a constant current driver and so no resistor is needed, all it would do is waste power.

You do however need a capacitor on the power input. The data sheet gives examples of both minimum and recommended connections for a range of operating modes.

I would also recommend adding a couple of resistors to the analog dimming input to bring the drive current down to about 200mA. You'll get a lot more life out of the parts if they aren't being driven right to the limit of their operating range and the change in brightness will be barely noticeable.