Impact is the one thing I would change about RDM, but my issue with it is not that it can fall off. 30 seconds is very long, so unless you chain ver procs or get hit by downtime you'll almost always be able to cast it. My issue with it is that it feels so tacked on. I serves to do nothing for our rotation and just feels like we're being forced to press a different button every second jolt for the sake of having an extra button to press. I'm more in favor of just having it as a rune IV style button replacement for jolt on proc, but making it a more infrequent but more powerful ability so you actually need to react to the procs and/or having it as another oGCD skill. You could even make it a ranged mana spender with a random cost to help unbalance our mana. Anything to make it more interesting.

As for acceleration, it's actually a nice skill since it allows new players to recover from unbalanced mana. For more experienced players, it becomes DPS cooldown that actually alters your rotation instead of just providing a boring % damage boost.