Since you should be weaving Light/Medium attacks between all skills this would only affect the very first cast of Endless Hail. By the time you got around to the second/third rotation Hawk Eye would be maxed and stay max for the remainder of the fight.

Trap beast and poison injection are both single-target debuffs, and caltrops and endless hail are ground-targets AoEs. The damage of single-target debuffs use the stats of the bar they were cast on, whereas the damage of ground targets use the stats of your current bar.*

Caltrops and endless hail are guaranteed to benefit from your front-bar stats, as a consequence. However, if you animation-cancel poison injection or rearming trap such that they don't actually impact the target until you're on your front-bar, you can sneak in another skill whose damage will be based on your [typically stronger] front-bar stats.

I'd actually recommend something like:

rearming trap > caltrops > endless hail > poison injection

*The exception is penetration... all skills use the penetration of the bar from which they were cast.

Poison Injection's damage is calculated based on the bar it impacts, thus if you've higher damage on your front bar, swap cancelling poison injection will make for a bit higher damage. Which makes it a skill I want to cast last on my back bar.