FA is very nice to have as it can save you in times when you are about to be overrun. However, only one point is needed to make good use of it. If you have a char that specializes in it, it can be very devastating in some areas. The problem is that later in the game, you run across a lot of cold immunes that will run right through it. It's also handy for quickly leveling your merc since they can stay alive to level against higher level monsters. The splash can keep whole groups of monsters at bay while you plug away at them.
IA is another matter, it was once an ber skill that was taken down quite a bit and you also have to hope the target does not walk away from the fire you started...they have to just sit there and fry. My preference is for exploding arrow simply because of the eye candy explosions...it also works very well with pierce since multiple explosions can go off. If you want to get the skill without using any points, get a Kuko and blast away by using the normal attack mode.
I have a zon who wears full Mav's set, which is a cold zons best friend. I maxed FA and strafe on her. Maxed FA does incredible amounts of damage. She keeps Baals minions at bay the entire time. She never has to run away! But 1 point is enough for most zons to freeze monsters.