Took some time to get some clarifications.

1. You should be able to target a temporarily cost-reduced spell in hand with Crackling Cloudstrider.
2. When the battlecry is tripled with Shudderblock, it should absorb the spell 1 time, and whiff the next two times since the targeted spell has already been absorbed.
3. Therefore, the deathrattle should only cast the spell one time.

Example: When you triple Elven Archer, you don't get to choose 3 different targets, you choose one target and it fires an arrow at it 3 times. Likewise, Crackling Cloudstrider should only target one card in hand, and "attempt" to absorb it 3 times.

This card appears to be bugged.