Level 15 of Poison Arrows is listed in the game as doing 619.5 dps for 3 seconds.


Loading a level 34 save before defeating Keara, I headed back to the battle tower to remove all retaliation enchantments from jewellery (and put a level 10 healing aura on anything that didn't have an existing healing aura on it), and learned level 10 of Poison Arrows (I already had Explosive Arrows at level 10), which is listed as 147 dps for 6 seconds. My stats at this point were 60 Dexterity and 7 Intelligence. I killed Keara a couple times with Poison Arrows and Explosive Arrows, then boosted either dexterity or intelligence and repeated.
Unfortunately, I forgot to learn Confusion, or I could have checked if it ever kicked in.

I moved out of Keara's line of fire to try to keep the combat log from becoming too cluttered. A side effect to this was that fights could vary in length, especially if she decided to go the long way around the room to get to me. That in turn meant she would vary in the amount she healed, so the damage required to kill her was not consistent. Random critical hits were also a factor.


For Poison Arrows, there was no significant difference between my base stats and boosting dexterity or intelligence. Critical hits didn't show any clear difference either, but there were not enough of them to get a decent sample size (I included the average and standard deviations below, anyway), and the values had a fairly large range.
The total number of hits required to kill Keara were pretty consistent, regardless of stats.

Code
Poison Arrows        base          100 Dex        93 Int

Hits to kill         8, 9           7, 9           8, 9

normal hits          14             11             13
critical hits         3              5              4

normal ave         304 ±  31      326 ±  20      327 ± 26
critical ave       797 ± 110      908 ± 100      919 ± 32



For Explosive Arrows, there was no variation in damage in any of the tests; all normal and all critical hits did the same amount. The number of critical hits was fairly consistent, excluding a Death Blow delivered once both times I killed Keara with my intelligence boosted.
At least the second time I defeated Keara with dexterity boosted she took the long way around the room once and delayed coming after me a couple times, so that (and the 1 less critical hit) accounts for the extra shots required to defeat her.

Code
Explosive Arrows    base         100 Dex         93 Int

Hits to kill       10, 12         12, 14         10, 11

normal hits          12             17              9
critical hits        10              9             10 (+ 2 Death Blows)

normal damage        387            387            387
critical damage     1017           1017           1017



Based on this, I would say active ranger skills do not get a damage bonus from your stats.