Just did a quick respec:

1 point - 10 mana, 12.5 sec. cool-down, 4m area, 43-57 damage + knock-back + stun
2 points - 10 mana, 10.5 sec. cool-down, 6m area, 43-57 damage + knock-back + stun
3 points - 10 mana, 10.5 sec. cool-down, 8m area, 57-71 damage + knock-back + stun
4 points - 10 mana, 8.5 sec. cool-down, 8m area, 57-71 damage + knock-back + stun
5 points - 10 mana, 8.5 sec. cool-down, 8m area, 68-85 damage + knock-back + stun

So, some points affect range, some cool-down period and some damage. The only two times that affect more than one aspect is when you put the second point in--shorter cool-down and bigger area of effect and the third point--bigger area and more damage. But you don't go down in either area or damage, only up.