I can only agree! taking in care also the passives, at lvl 50 youll have the buff on for like 10 - 11 sec. In case you choose the movement speed morph, youll have like 7 - 7,5 sec in the form. The gap between these two scales ofc. So in PvE - only Thundering Presence.Don't get the speed bonus for storm form. The added duration is much better, saves you a ton of mana in the long run whereas the speed boost in combat is greatly diminished.