Hmm, not bad ideas, here's my take on them though:

Cloaked Arrow: Arrow appears a short distance from the targeted point, and then travels away from you a slightly longer distance, dealing high damage to the first enemy hit, and then less as it passes through more enemies. Higher levels increase the range, distance traveled, and damage, and decrease the rate at which damage falls off from multiple targets. Cooldown ~5-10 seconds, low-moderate mana cost.

Chain Reaction: Applies a DoT effect that lasts 5 seconds. After 4 seconds, the effect jumps to another enemy, this time lasting 4 seconds, and jumping after 3, and then 3 seconds jumping after 2. When the DoT effect ends, the unit explodes, dealing damage to nearby enemies, and is stunned for 3 seconds. Higher levels decrease the rate at which the duration decreases, causing the effect to jump more. Cooldown ~15-20 seconds, moderate mana cost.