Runspeed in some form can be very useful in PvE encounters even if the movement requirements seem very light.
- Icewalker is ~20 dps more then Cat's Speed
- Icewalker is ~25 dps more then Tuskarr's Speed
From those facts we can derive roughly how much time has to be spent in motion per encounter for runspeed to be more dps then the alternatives.
So for a shaman outputting 5000dps on a 5 minute encounter they will have to spend at least 15 seconds in motion for Cat's Speed to be superior to Icewalker.
For this reason it is recommended that raiding shaman keep two pairs of boots. One pair with some form of runspeed and one pair with either an Icewalker
or a Greater Assault
or (if they are an engineer)
a Nitro Boosts
enchant. That way the proper boot enchant to use can be determined by the encounter.